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1.
Proc Natl Acad Sci U S A ; 121(34): e2400912121, 2024 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-39145930

RESUMO

Myo-inositol-1-phosphate synthase (MIPS) catalyzes the NAD+-dependent isomerization of glucose-6-phosphate (G6P) into inositol-1-phosphate (IMP), controlling the rate-limiting step of the inositol pathway. Previous structural studies focused on the detailed molecular mechanism, neglecting large-scale conformational changes that drive the function of this 240 kDa homotetrameric complex. In this study, we identified the active, endogenous MIPS in cell extracts from the thermophilic fungus Thermochaetoides thermophila. By resolving the native structure at 2.48 Å (FSC = 0.143), we revealed a fully populated active site. Utilizing 3D variability analysis, we uncovered conformational states of MIPS, enabling us to directly visualize an order-to-disorder transition at its catalytic center. An acyclic intermediate of G6P occupied the active site in two out of the three conformational states, indicating a catalytic mechanism where electrostatic stabilization of high-energy intermediates plays a crucial role. Examination of all isomerases with known structures revealed similar fluctuations in secondary structure within their active sites. Based on these findings, we established a conformational selection model that governs substrate binding and eventually inositol availability. In particular, the ground state of MIPS demonstrates structural configurations regardless of substrate binding, a pattern observed across various isomerases. These findings contribute to the understanding of MIPS structure-based function, serving as a template for future studies targeting regulation and potential therapeutic applications.


Assuntos
Domínio Catalítico , Inositol , Mio-Inositol-1-Fosfato Sintase , Mio-Inositol-1-Fosfato Sintase/metabolismo , Mio-Inositol-1-Fosfato Sintase/genética , Mio-Inositol-1-Fosfato Sintase/química , Inositol/metabolismo , Inositol/química , Fosfatos de Inositol/metabolismo , Glucose-6-Fosfato/metabolismo , Glucose-6-Fosfato/química , Modelos Moleculares , Conformação Proteica , Proteínas Fúngicas/metabolismo , Proteínas Fúngicas/química
2.
Mol Metab ; 88: 102018, 2024 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-39182844

RESUMO

OBJECTIVE: Glucose-1,6-bisphosphate (G-1,6-BP), a byproduct of glycolysis that is synthesized by phosphoglucomutase 2 like 1 (PGM2L1), is particularly abundant in neurons. G-1,6-BP is sensitive to the glycolytic flux, due to its dependence on 1,3-bisphosphoglycerate as phosphate donor, and the energy state, due to its degradation by inosine monophosphate-activated phosphomannomutase 1. Since the exact role of this metabolite remains unclear, our aim was to elucidate the specific function of G-1,6-BP in the brain. METHODS: The effect of PGM2L1 on neuronal post-ischemic viability was assessed by siRNA-mediated knockdown of PGM2L1 in primary mouse neurons. Acute mouse brain slices were used to correlate the reduction in G-1,6-BP upon ischemia to changes in carbon metabolism by 13C6-glucose tracing. A drug affinity responsive target stability assay was used to test if G-1,6-BP interacts with the mitochondrial pyruvate carrier (MPC) subunits in mouse brain protein extracts. Human embryonic kidney cells expressing a MPC bioluminescence resonance energy transfer sensor were used to analyze how PGM2L1 overexpression affects MPC activity. The effect of G-1,6-BP on mitochondrial pyruvate uptake and oxygen consumption rates was analyzed in isolated mouse brain mitochondria. PGM2L1 and a predicted upstream kinase were overexpressed in a human neuroblastoma cell line and G-1,6-BP levels were measured. RESULTS: We found that G-1,6-BP in mouse brain slices was quickly degraded upon ischemia and reperfusion. Knockdown of PGM2L1 in mouse neurons reduced post-ischemic viability, indicating that PGM2L1 plays a neuroprotective role. The reduction in G-1,6-BP upon ischemia was not accompanied by alterations in glycolytic rates but we did see a reduced 13C6-glucose incorporation into citrate, suggesting a potential role in mitochondrial pyruvate uptake or metabolism. Indeed, G-1,6-BP interacted with both MPC subunits and overexpression of PGM2L1 increased MPC activity. G-1,6-BP, at concentrations found in the brain, enhanced mitochondrial pyruvate uptake and pyruvate-induced oxygen consumption rates. Overexpression of a predicted upstream kinase inhibited PGM2L1 activity, showing that besides metabolism, also signaling pathways can regulate G-1,6-BP levels. CONCLUSIONS: We provide evidence that G-1,6-BP positively regulates mitochondrial pyruvate uptake and post-ischemic neuronal viability. These compelling data reveal a novel mechanism by which neurons can couple glycolysis-derived pyruvate to the tricarboxylic acid cycle. This process is sensitive to the glycolytic flux, the cell's energetic state, and upstream signaling cascades, offering many regulatory means to fine-tune this critical metabolic step.


Assuntos
Encéfalo , Mitocôndrias , Neurônios , Animais , Camundongos , Mitocôndrias/metabolismo , Humanos , Neurônios/metabolismo , Encéfalo/metabolismo , Ácido Pirúvico/metabolismo , Camundongos Endogâmicos C57BL , Masculino , Glicólise , Glucose-6-Fosfato/metabolismo , Glucose/metabolismo , Células HEK293 , Proteínas de Transporte da Membrana Mitocondrial/metabolismo , Proteínas de Transporte da Membrana Mitocondrial/genética
3.
Commun Biol ; 7(1): 909, 2024 Jul 27.
Artigo em Inglês | MEDLINE | ID: mdl-39068257

RESUMO

Metabolic regulation occurs through precise control of enzyme activity. Allomorphy is a post-translational fine control mechanism where the catalytic rate is governed by a conformational switch that shifts the enzyme population between forms with different activities. ß-Phosphoglucomutase (ßPGM) uses allomorphy in the catalysis of isomerisation of ß-glucose 1-phosphate to glucose 6-phosphate via ß-glucose 1,6-bisphosphate. Herein, we describe structural and biophysical approaches to reveal its allomorphic regulatory mechanism. Binding of the full allomorphic activator ß-glucose 1,6-bisphosphate stimulates enzyme closure, progressing through NAC I and NAC III conformers. Prior to phosphoryl transfer, loops positioned on the cap and core domains are brought into close proximity, modulating the environment of a key proline residue. Hence accelerated isomerisation, likely via a twisted anti/C4-endo transition state, leads to the rapid predominance of active cis-P ßPGM. In contrast, binding of the partial allomorphic activator fructose 1,6-bisphosphate arrests ßPGM at a NAC I conformation and phosphoryl transfer to both cis-P ßPGM and trans-P ßPGM occurs slowly. Thus, allomorphy allows a rapid response to changes in food supply while not otherwise impacting substantially on levels of important metabolites.


Assuntos
Domínio Catalítico , Fosfoglucomutase , Prolina , Fosfoglucomutase/metabolismo , Fosfoglucomutase/química , Fosfoglucomutase/genética , Prolina/metabolismo , Prolina/química , Isomerismo , Glucofosfatos/metabolismo , Conformação Proteica , Humanos , Catálise , Modelos Moleculares , Glucose-6-Fosfato/análogos & derivados
4.
Mol Cell ; 84(14): 2732-2746.e5, 2024 Jul 25.
Artigo em Inglês | MEDLINE | ID: mdl-38981483

RESUMO

Metabolic enzymes can adapt during energy stress, but the consequences of these adaptations remain understudied. Here, we discovered that hexokinase 1 (HK1), a key glycolytic enzyme, forms rings around mitochondria during energy stress. These HK1-rings constrict mitochondria at contact sites with the endoplasmic reticulum (ER) and mitochondrial dynamics protein (MiD51). HK1-rings prevent mitochondrial fission by displacing the dynamin-related protein 1 (Drp1) from mitochondrial fission factor (Mff) and mitochondrial fission 1 protein (Fis1). The disassembly of HK1-rings during energy restoration correlated with mitochondrial fission. Mechanistically, we identified that the lack of ATP and glucose-6-phosphate (G6P) promotes the formation of HK1-rings. Mutations that affect the formation of HK1-rings showed that HK1-rings rewire cellular metabolism toward increased TCA cycle activity. Our findings highlight that HK1 is an energy stress sensor that regulates the shape, connectivity, and metabolic activity of mitochondria. Thus, the formation of HK1-rings may affect mitochondrial function in energy-stress-related pathologies.


Assuntos
Dinaminas , Metabolismo Energético , Hexoquinase , Mitocôndrias , Dinâmica Mitocondrial , Proteínas Mitocondriais , Hexoquinase/metabolismo , Hexoquinase/genética , Humanos , Mitocôndrias/metabolismo , Mitocôndrias/genética , Mitocôndrias/enzimologia , Dinaminas/metabolismo , Dinaminas/genética , Proteínas Mitocondriais/metabolismo , Proteínas Mitocondriais/genética , Animais , Trifosfato de Adenosina/metabolismo , Estresse Fisiológico , Retículo Endoplasmático/metabolismo , Proteínas de Membrana/metabolismo , Proteínas de Membrana/genética , Ciclo do Ácido Cítrico , Glucose-6-Fosfato/metabolismo , Camundongos , Células HeLa , Células HEK293 , GTP Fosfo-Hidrolases/metabolismo , GTP Fosfo-Hidrolases/genética , Mutação
5.
PLoS Pathog ; 20(6): e1011979, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38900808

RESUMO

The cell surface of Toxoplasma gondii is rich in glycoconjugates which hold diverse and vital functions in the lytic cycle of this obligate intracellular parasite. Additionally, the cyst wall of bradyzoites, that shields the persistent form responsible for chronic infection from the immune system, is heavily glycosylated. Formation of glycoconjugates relies on activated sugar nucleotides, such as uridine diphosphate N-acetylglucosamine (UDP-GlcNAc). The glucosamine-phosphate-N-acetyltransferase (GNA1) generates N-acetylglucosamine-6-phosphate critical to produce UDP-GlcNAc. Here, we demonstrate that downregulation of T. gondii GNA1 results in a severe reduction of UDP-GlcNAc and a concomitant drop in glycosylphosphatidylinositols (GPIs), leading to impairment of the parasite's ability to invade and replicate in the host cell. Surprisingly, attempts to rescue this defect through exogenous GlcNAc supplementation fail to completely restore these vital functions. In depth metabolomic analyses elucidate diverse causes underlying the failed rescue: utilization of GlcNAc is inefficient under glucose-replete conditions and fails to restore UDP-GlcNAc levels in GNA1-depleted parasites. In contrast, GlcNAc-supplementation under glucose-deplete conditions fully restores UDP-GlcNAc levels but fails to rescue the defects associated with GNA1 depletion. Our results underscore the importance of glucosamine-6-phosphate acetylation in governing T. gondii replication and invasion and highlight the potential of the evolutionary divergent GNA1 in Apicomplexa as a target for the development of much-needed new therapeutic strategies.


Assuntos
Acetilglucosamina , Glucose-6-Fosfato , Toxoplasma , Toxoplasma/metabolismo , Glucose-6-Fosfato/metabolismo , Glucose-6-Fosfato/análogos & derivados , Acetilglucosamina/metabolismo , Acetilação , Animais , Glucosamina 6-Fosfato N-Acetiltransferase/metabolismo , Humanos , Glucosamina/metabolismo , Glucosamina/análogos & derivados , Camundongos , Toxoplasmose/metabolismo , Toxoplasmose/parasitologia , Proteínas de Protozoários/metabolismo , Proteínas de Protozoários/genética
6.
Free Radic Biol Med ; 222: 505-518, 2024 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-38848786

RESUMO

The oxidative phase of the pentose phosphate pathway (PPP) involving the enzymes glucose-6-phosphate dehydrogenase (G6PDH), 6-phosphogluconolactonase (6PGL), and 6-phosphogluconate dehydrogenase (6PGDH), is critical to NADPH generation within cells, with these enzymes catalyzing the conversion of glucose-6-phosphate (G6P) into ribulose-5-phosphate (Ribu5-P). We have previously studied peroxyl radical (ROO•) mediated oxidative inactivation of E. coli G6PDH, 6PGL, and 6PGDH. However, these data were obtained from experiments where each enzyme was independently exposed to ROO•, a condition not reflecting biological reality. In this work we investigated how NADPH production is modulated when these enzymes are jointly exposed to ROO•. Enzyme mixtures (1:1:1 ratio) were exposed to ROO• produced from thermolysis of 100 mM 2,2'-azobis(2-methylpropionamidine) dihydrochloride (AAPH). NADPH was quantified at 340 nm, and protein oxidation analyzed by liquid chromatography with mass spectrometric detection (LC-MS). The data obtained were rationalized using a mathematical model. The mixture of non-oxidized enzymes, G6P and NADP+ generated ∼175 µM NADPH. Computational simulations showed a constant decrease of G6P associated with NADPH formation, consistent with experimental data. When the enzyme mixture was exposed to AAPH (3 h, 37 °C), lower levels of NADPH were detected (∼100 µM) which also fitted with computational simulations. LC-MS analyses indicated modifications at Tyr, Trp, and Met residues but at lower concentrations than detected for the isolated enzymes. Quantification of NADPH generation showed that the pathway activity was not altered during the initial stages of the oxidations, consistent with a buffering role of G6PDH towards inactivation of the oxidative phase of the pathway.


Assuntos
Escherichia coli , Glucosefosfato Desidrogenase , NADP , Oxirredução , Via de Pentose Fosfato , Fosfogluconato Desidrogenase , Glucosefosfato Desidrogenase/metabolismo , Fosfogluconato Desidrogenase/metabolismo , NADP/metabolismo , Escherichia coli/metabolismo , Escherichia coli/genética , Ribulosefosfatos/metabolismo , Glucose-6-Fosfato/metabolismo , Peróxidos/metabolismo , Hidrolases de Éster Carboxílico
7.
Bioresour Technol ; 406: 130999, 2024 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-38885721

RESUMO

Microalgae-based biotechnology holds significant potential for addressing dual challenges of phosphorus removal and recovery from wastewater; however, the removal mechanism and metabolic adaptation of microalgae to dissolved organic phosphorus (DOP) are still unclear. This study investigated the removal mechanisms and metabolomic responses of the Chlorella pyrenoidosa to different DOP forms, including adenosine triphosphate (ATP), glucose-6-phosphate (G-6-P), and ß-glycerophosphate (ß-GP). The results showed C. pyrenoidosa could efficiently take up above 96% DOP through direct transport and post-hydrolysis pathways. The uptake of inorganic phosphorus (IP) followed pseudo first order kinetic model, while DOP followed pseudo second order kinetic model. Metabolite profiling revealed substantial alterations in central carbon metabolism depending on the DOP source. G-6-P upregulated glycolytic and TCA cycle intermediates, reflecting enhanced carbohydrates, amino acids and nucleotides biosynthesis. In contrast, ATP down-regulated carbohydrate and purine metabolism, inhibiting sustainable growth of microalgae. This study offers theoretical support for phosphorus-containing wastewater treatment using microalgae.


Assuntos
Trifosfato de Adenosina , Chlorella , Fósforo , Chlorella/metabolismo , Fósforo/metabolismo , Trifosfato de Adenosina/metabolismo , Microalgas/metabolismo , Cinética , Glucose-6-Fosfato/metabolismo
8.
Sci Rep ; 14(1): 10682, 2024 05 09.
Artigo em Inglês | MEDLINE | ID: mdl-38724517

RESUMO

Choy Sum, a stalk vegetable highly valued in East and Southeast Asia, is characterized by its rich flavor and nutritional profile. Metabolite accumulation is a key factor in Choy Sum stalk development; however, no research has focused on metabolic changes during the development of Choy Sum, especially in shoot tip metabolites, and their effects on growth and flowering. Therefore, in the present study, we used a widely targeted metabolomic approach to analyze metabolites in Choy Sum stalks at the seedling (S1), bolting (S3), and flowering (S5) stages. In total, we identified 493 metabolites in 31 chemical categories across all three developmental stages. We found that the levels of most carbohydrates and amino acids increased during stalk development and peaked at S5. Moreover, the accumulation of amino acids and their metabolites was closely related to G6P, whereas the expression of flowering genes was closely related to the content of T6P, which may promote flowering by upregulating the expressions of BcSOC1, BcAP1, and BcSPL5. The results of this study contribute to our understanding of the relationship between the accumulation of stem tip substances during development and flowering and of the regulatory mechanisms of stalk development in Choy Sum and other related species.


Assuntos
Brassica , Flores , Regulação da Expressão Gênica de Plantas , Brassica/química , Brassica/genética , Brassica/crescimento & desenvolvimento , Brassica/metabolismo , Flores/crescimento & desenvolvimento , Flores/metabolismo , Metaboloma , Caules de Planta/química , Caules de Planta/crescimento & desenvolvimento , Transcriptoma , Carboidratos , Proteínas de Plantas/genética , Glucose-6-Fosfato/metabolismo , Genes de Plantas
9.
Biochem Biophys Res Commun ; 716: 150030, 2024 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-38704889

RESUMO

Sugar phosphates are potential sources of carbon and phosphate for bacteria. Despite that the process of internalization of Glucose-6-Phosphate (G6P) through plasma membrane remained elusive in several bacteria. VCA0625-27, made of periplasmic ligand binding protein (PLBP) VCA0625, an atypical monomeric permease VCA0626, and a cytosolic ATPase VCA0627, recently emerged as hexose-6-phosphate uptake system of Vibrio cholerae. Here we report high resolution crystal structure of VCA0625 in G6P bound state that largely resembles AfuA of Actinobacillus pleuropneumoniae. MD simulations on VCA0625 in apo and G6P bound states unraveled an 'open to close' and swinging bi-lobal motions, which are diminished upon G6P binding. Mutagenesis followed by biochemical assays on VCA0625 underscored that R34 works as gateway to bind G6P. Although VCA0627 binds ATP, it is ATPase deficient in the absence of VCA0625 and VCA0626, which is a signature phenomenon of type-I ABC importer. Further, modeling, docking and systematic sequence analysis allowed us to envisage the existence of similar atypical type-I G6P importer with fused monomeric permease in 27 other gram-negative bacteria.


Assuntos
Transportadores de Cassetes de Ligação de ATP , Proteínas de Bactérias , Glucose-6-Fosfato , Vibrio cholerae , Transportadores de Cassetes de Ligação de ATP/metabolismo , Transportadores de Cassetes de Ligação de ATP/química , Transportadores de Cassetes de Ligação de ATP/genética , Proteínas de Bactérias/química , Proteínas de Bactérias/metabolismo , Proteínas de Bactérias/genética , Sítios de Ligação , Cristalografia por Raios X , Glucose-6-Fosfato/metabolismo , Glucose-6-Fosfato/química , Modelos Moleculares , Simulação de Dinâmica Molecular , Ligação Proteica , Conformação Proteica , Vibrio cholerae/metabolismo , Vibrio cholerae/genética
10.
Plant Mol Biol ; 114(3): 60, 2024 May 17.
Artigo em Inglês | MEDLINE | ID: mdl-38758412

RESUMO

Pyruvate kinase (Pyk, EC 2.7.1.40) is a glycolytic enzyme that generates pyruvate and adenosine triphosphate (ATP) from phosphoenolpyruvate (PEP) and adenosine diphosphate (ADP), respectively. Pyk couples pyruvate and tricarboxylic acid metabolisms. Synechocystis sp. PCC 6803 possesses two pyk genes (encoded pyk1, sll0587 and pyk2, sll1275). A previous study suggested that pyk2 and not pyk1 is essential for cell viability; however, its biochemical analysis is yet to be performed. Herein, we biochemically analyzed Synechocystis Pyk2 (hereafter, SyPyk2). The optimum pH and temperature of SyPyk2 were 7.0 and 55 °C, respectively, and the Km values for PEP and ADP under optimal conditions were 1.5 and 0.053 mM, respectively. SyPyk2 is activated in the presence of glucose-6-phosphate (G6P) and ribose-5-phosphate (R5P); however, it remains unaltered in the presence of adenosine monophosphate (AMP) or fructose-1,6-bisphosphate. These results indicate that SyPyk2 is classified as PykA type rather than PykF, stimulated by sugar monophosphates, such as G6P and R5P, but not by AMP. SyPyk2, considering substrate affinity and effectors, can play pivotal roles in sugar catabolism under nonphotosynthetic conditions.


Assuntos
Glucose-6-Fosfato , Fosfoenolpiruvato , Piruvato Quinase , Ribosemonofosfatos , Synechocystis , Synechocystis/metabolismo , Synechocystis/genética , Piruvato Quinase/metabolismo , Piruvato Quinase/genética , Fosfoenolpiruvato/metabolismo , Glucose-6-Fosfato/metabolismo , Ribosemonofosfatos/metabolismo , Especificidade por Substrato , Concentração de Íons de Hidrogênio , Proteínas de Bactérias/metabolismo , Proteínas de Bactérias/genética , Cinética , Temperatura
11.
New Phytol ; 242(6): 2453-2463, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38567702

RESUMO

CO2 release in the light (RL) and its presumed source, oxidative pentose phosphate pathways, were found to be insensitive to CO2 concentration. The oxidative pentose phosphate pathways form glucose 6-phosphate (G6P) shunts that bypass the nonoxidative pentose phosphate reactions of the Calvin-Benson cycle. Using adenosine diphosphate glucose and uridine diphosphate glucose as proxies for labeling of G6P in the stroma and cytosol respectively, it was found that only the cytosolic shunt was active. Uridine diphosphate glucose, a proxy for cytosolic G6P, and 6-phosphogluconate (6PG) were significantly less labeled than Calvin-Benson cycle intermediates in the light. But ADP glucose, a proxy for stromal G6P, is labeled to the same degree as Calvin-Benson cycle intermediates and much greater than 6PG. A metabolically inert pool of sedoheptulose bisphosphate can slowly equilibrate keeping the label in sedoheptulose lower than in other stromal metabolites. Finally, phosphorylation of fructose 6-phosphate (F6P) in the cytosol can allow some unlabeled carbon in cytosolic F6P to dilute label in phosphenolpyruvate. The results clearly show that there is oxidative pentose phosphate pathway activity in the cytosol that provides a shunt around the nonoxidative pentose phosphate pathway reactions of the Calvin-Benson cycle and is not strongly CO2-sensitive.


Assuntos
Dióxido de Carbono , Oxirredução , Via de Pentose Fosfato , Fotossíntese , Dióxido de Carbono/metabolismo , Glucose-6-Fosfato/metabolismo , Citosol/metabolismo , Luz , Arabidopsis/metabolismo , Arabidopsis/fisiologia
12.
Chemistry ; 30(28): e202400690, 2024 May 17.
Artigo em Inglês | MEDLINE | ID: mdl-38471074

RESUMO

Droplet formation via liquid-liquid phase separation is thought to be involved in the regulation of various biological processes, including enzymatic reactions. We investigated a glycolytic enzymatic reaction, the conversion of glucose-6-phosphate to 6-phospho-D-glucono-1,5-lactone with concomitant reduction of NADP+ to NADPH both in the absence and presence of dynamically controlled liquid droplet formation. Here, the nucleotide serves as substrate as well as the scaffold required for the formation of liquid droplets. To further expand the process parameter space, temperature and pressure dependent measurements were performed. Incorporation of the reactants in the liquid droplet phase led to a boost in enzymatic activity, which was most pronounced at medium-high pressures. The crowded environment of the droplet phase induced a marked increase of the affinity of the enzyme and substrate. An increase in turnover number in the droplet phase at high pressure contributed to a further strong increase in catalytic efficiency. Enzyme systems that are dynamically coupled to liquid condensate formation may be the key to deciphering many biochemical reactions. Expanding the process parameter space by adjusting temperature and pressure conditions can be a means to further increase the efficiency of industrial enzyme utilization and help uncover regulatory mechanisms adopted by extremophiles.


Assuntos
Glucosefosfato Desidrogenase , Pressão , Ativação Enzimática , Gluconatos/metabolismo , Gluconatos/química , Glucose-6-Fosfato/metabolismo , Glucose-6-Fosfato/química , Glucosefosfato Desidrogenase/metabolismo , Glucosefosfato Desidrogenase/química , Cinética , Lactonas/química , Lactonas/metabolismo , NADP/metabolismo , NADP/química , Temperatura
13.
Mol Metab ; 79: 101838, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-37995884

RESUMO

OBJECTIVE: Carbohydrate Response Element Binding Protein (ChREBP) is a glucose 6-phosphate (G6P)-sensitive transcription factor that acts as a metabolic switch to maintain intracellular glucose and phosphate homeostasis. Hepatic ChREBP is well-known for its regulatory role in glycolysis, the pentose phosphate pathway, and de novo lipogenesis. The physiological role of ChREBP in hepatic glycogen metabolism and blood glucose regulation has not been assessed in detail, and ChREBP's contribution to carbohydrate flux adaptations in hepatic Glycogen Storage Disease type 1 (GSD I) requires further investigation. METHODS: The current study aimed to investigate the role of ChREBP as a regulator of glycogen metabolism in response to hepatic G6P accumulation, using a model for acute hepatic GSD type Ib. The immediate biochemical and regulatory responses to hepatic G6P accumulation were evaluated upon G6P transporter inhibition by the chlorogenic acid S4048 in mice that were either treated with a short hairpin RNA (shRNA) directed against ChREBP (shChREBP) or a scrambled shRNA (shSCR). Complementary stable isotope experiments were performed to quantify hepatic carbohydrate fluxes in vivo. RESULTS: ShChREBP treatment normalized the S4048-mediated induction of hepatic ChREBP target genes to levels observed in vehicle- and shSCR-treated controls. In parallel, hepatic shChREBP treatment in S4048-infused mice resulted in a more pronounced accumulation of hepatic glycogen and further reduction of blood glucose levels compared to shSCR treatment. Hepatic ChREBP knockdown modestly increased glucokinase (GCK) flux in S4048-treated mice while it enhanced UDP-glucose turnover as well as glycogen synthase and phosphorylase fluxes. Hepatic GCK mRNA and protein levels were induced by shChREBP treatment in both vehicle- and S4048-treated mice, while glycogen synthase 2 (GYS2) and glycogen phosphorylase (PYGL) mRNA and protein levels were reduced. Finally, knockdown of hepatic ChREBP expression reduced starch domain binding protein 1 (STBD1) mRNA and protein levels while it inhibited acid alpha-glucosidase (GAA) activity, suggesting reduced capacity for lysosomal glycogen breakdown. CONCLUSIONS: Our data show that ChREBP activation controls hepatic glycogen and blood glucose levels in acute hepatic GSD Ib through concomitant regulation of glucose phosphorylation, glycogenesis, and glycogenolysis. ChREBP-mediated control of GCK enzyme levels aligns with corresponding adaptations in GCK flux. In contrast, ChREBP activation in response to acute hepatic GSD Ib exerts opposite effects on GYS2/PYGL enzyme levels and their corresponding fluxes, indicating that GYS2/PYGL expression levels are not limiting to their respective fluxes under these conditions.


Assuntos
Glicemia , Doença de Depósito de Glicogênio Tipo I , Animais , Camundongos , Metabolismo dos Carboidratos , Modelos Animais de Doenças , Glucose/metabolismo , Glucose-6-Fosfato/metabolismo , Glicogênio/metabolismo , Glicogênio Sintase/metabolismo , Glicogênio Hepático/metabolismo , Fosfatos , RNA Mensageiro/metabolismo , RNA Interferente Pequeno/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo
14.
Protein Expr Purif ; 215: 106408, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38008389

RESUMO

Hexokinases (HKs) play a vital role in glucose metabolism, which controls the first committed step catalyzing the production of glucose-6-phosphate from glucose. Two HKs (CGIHK1 and CGIHK2) from the Pacific oyster Crassostrea giga were cloned and characterized. CGIHK1 and CGIHK2 were recombinantly expressed in Escherichia coli and successfully purified by the Ni-NTA column. The optimum pH of the two enzymes was pH 8.0 and 8.5, respectively. The optimum temperature of the two enzymes was 42 °C and 50 °C, respectively. Both enzymes showed a clear requirement for divalent magnesium and were strongly inhibited by SDS. CGIHK1 exhibited highly strict substrate specificity to glucose, while CGIHK2 could also catalyze other 11 monosaccharide substrates. This is the first report on the in vitro biosynthesis of glucose-6-phosphate by the hexokinases from Crassostrea gigas. The facile expression and purification procedures combined with different substrate specificities make CGIHK1 and CGIHK2 candidates for the biosynthesis of glucose-6-phosphate and other sugar-phosphates.


Assuntos
Crassostrea , Hexoquinase , Animais , Hexoquinase/metabolismo , Crassostrea/genética , Glucose-6-Fosfato/metabolismo , Temperatura , Glucose/metabolismo
15.
Carbohydr Res ; 534: 108979, 2023 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-37931349

RESUMO

ß-phosphoglucomutase (ßPGM) catalyzes the conversion of ß-glucose 1-phosphate (ßG1P) to glucose-6-phosphate (G6P), a universal source of cellular energy, in a two-step process. Transition state analogue (TSA) complexes formed from substrate analogues and a metal fluoride (MgF3- and AlF4-) enable analysis of each of these enzymatic steps independently. Novel substrate analogues incorporating fluorine offer opportunities to interrogate the enzyme mechanism using 19F NMR spectroscopy. Herein, the synthesis of a novel fluorinated phosphonyl C-glycoside (3-deoxy-3-fluoro-ß-d-glucopyranosyl)methylphosphonate (1), in 12 steps (0.85 % overall yield) is disclosed. A four-stage synthetic strategy was employed, involving: 1) fluorine addition to the monosaccharide, 2) selective anomeric deprotection, 3) phosphonylation of the anomeric centre, and 4) global deprotection. Analysis of ßPGM and 1 will be reported in due course.


Assuntos
Flúor , Fosfoglucomutase , Fosfoglucomutase/química , Flúor/química , Glucose-6-Fosfato
16.
Development ; 150(20)2023 10 15.
Artigo em Inglês | MEDLINE | ID: mdl-37842778

RESUMO

As photoautotrophic organisms, plants produce an incredible spectrum of pigments, anti-herbivory compounds, structural materials and energic intermediates. These biosynthetic routes help plants grow, reproduce and mitigate stress. HEXOKINASE1 (HXK1), a metabolic enzyme and glucose sensor, catalyzes the phosphorylation of hexoses, a key introductory step for many of these pathways. However, previous studies have largely focused on the glucose sensing and signaling functions of HXK1, and the importance of the enzyme's catalytic function is only recently being connected to plant development. In this brief Spotlight, we describe the developmental significance of plant HXK1 and its role in plant metabolic pathways, specifically in glucose-6-phosphate production. Furthermore, we describe the emerging connections between metabolism and development and suggest that HXK1 signaling and catalytic activity regulate discrete areas of plant development.


Assuntos
Glucose-6-Fosfato , Hexoquinase , Desenvolvimento Vegetal , Glucose/metabolismo , Hexoquinase/genética , Hexoquinase/metabolismo , Fosforilação , Plantas/metabolismo
17.
ACS Chem Biol ; 18(10): 2324-2334, 2023 10 20.
Artigo em Inglês | MEDLINE | ID: mdl-37793187

RESUMO

The glmS riboswitch is a motif found in 5'-untranslated regions of bacterial mRNA that controls the synthesis of glucosamine-6-phosphate (GlcN6P), an essential building block for the bacterial cell wall, by a feedback mechanism. Activation of the glmS riboswitch by GlcN6P mimics interferes with the ability of bacteria to synthesize its cell wall. Accordingly, GlcN6P mimics acting as glmS activators are promising candidates for future antibiotic drugs that may overcome emerging bacterial resistance against established antibiotics. We describe the synthesis of a series of phosphonate mimics of GlcN6P as well as the thiasugar analogue of GlcN6P. The phosphonate mimics differ in their pKa value to answer the question of whether derivatives with a pKa matching that of GlcN6P would be efficient glmS activators. We found that all derivatives activate the riboswitch, however, less efficiently than GlcN6P. This observation can be explained by the missing hydrogen bonds in the case of phosphonates and is valuable information for the design of future GlcN6P mimics. The thiasugar analogue of GlcN6P on the other hand turned out to be a glmS riboswitch activator with the same activity as the natural metabolite GlcN6P. The nonphosphorylated thiasugar displayed antimicrobial activity against certain bacilli. Therefore, the compound is a promising lead structure for the development of future antibiotics with a potentially novel mode of action.


Assuntos
Organofosfonatos , RNA Catalítico , Riboswitch , Proteínas de Bactérias/metabolismo , Organofosfonatos/farmacologia , Antibacterianos/farmacologia , Bactérias/metabolismo , Glucosamina , Glucose-6-Fosfato/metabolismo , Fosfatos , RNA Catalítico/química
18.
J Mol Endocrinol ; 71(4)2023 11 01.
Artigo em Inglês | MEDLINE | ID: mdl-37855366

RESUMO

In the endoplasmic reticulum (ER) lumen, glucose-6-phosphatase catalytic subunit 1 and 2 (G6PC1; G6PC2) hydrolyze glucose-6-phosphate (G6P) to glucose and inorganic phosphate whereas hexose-6-phosphate dehydrogenase (H6PD) hydrolyzes G6P to 6-phosphogluconate (6PG) in a reaction that generates NADPH. 11ß-hydroxysteroid dehydrogenase type 1 (HSD11B1) utilizes this NADPH to convert inactive cortisone to cortisol. HSD11B1 inhibitors improve insulin sensitivity whereas G6PC inhibitors are predicted to lower fasting blood glucose (FBG). This study investigated whether G6PC1 and G6PC2 influence G6P flux through H6PD and vice versa. Using a novel transcriptional assay that utilizes separate fusion genes to quantitate glucocorticoid and glucose signaling, we show that overexpression of H6PD and HSD11B1 in the islet-derived 832/13 cell line activated glucocorticoid-stimulated fusion gene expression. Overexpression of HSD11B1 blunted glucose-stimulated fusion gene expression independently of altered G6P flux. While overexpression of G6PC1 and G6PC2 blunted glucose-stimulated fusion gene expression, it had minimal effect on glucocorticoid-stimulated fusion gene expression. In the liver-derived HepG2 cell line, overexpression of H6PD and HSD11B1 activated glucocorticoid-stimulated fusion gene expression but overexpression of G6PC1 and G6PC2 had no effect. In rodents, HSD11B1 converts 11-dehydrocorticosterone (11-DHC) to corticosterone. Studies in wild-type and G6pc2 knockout mice treated with 11-DHC for 5 weeks reveal metabolic changes unaffected by the absence of G6PC2. These data suggest that HSD11B1 activity is not significantly affected by the presence or absence of G6PC1 or G6PC2. As such, G6PC1 and G6PC2 inhibitors are predicted to have beneficial effects by reducing FBG without causing a deleterious increase in glucocorticoid signaling.


Assuntos
Glucocorticoides , Glucose-6-Fosfato , Animais , Camundongos , 11-beta-Hidroxiesteroide Desidrogenase Tipo 1/genética , 11-beta-Hidroxiesteroide Desidrogenase Tipo 1/metabolismo , Linhagem Celular , Glucocorticoides/farmacologia , Glucocorticoides/metabolismo , Glucose/metabolismo , Glucose-6-Fosfato/metabolismo , NADP/metabolismo , Humanos
19.
Nat Commun ; 14(1): 3835, 2023 06 28.
Artigo em Inglês | MEDLINE | ID: mdl-37380648

RESUMO

Takotsubo cardiomyopathy is a stress-induced cardiovascular disease with symptoms comparable to those of an acute coronary syndrome but without coronary obstruction. Takotsubo was initially considered spontaneously reversible, but epidemiological studies revealed significant long-term morbidity and mortality, the reason for which is unknown. Here, we show in a female rodent model that a single pharmacological challenge creates a stress-induced cardiomyopathy similar to Takotsubo. The acute response involves changes in blood and tissue biomarkers and in cardiac in vivo imaging acquired with ultrasound, magnetic resonance and positron emission tomography. Longitudinal follow up using in vivo imaging, histochemistry, protein and proteomics analyses evidences a continued metabolic reprogramming of the heart towards metabolic malfunction, eventually leading to irreversible damage in cardiac function and structure. The results combat the supposed reversibility of Takotsubo, point to dysregulation of glucose metabolic pathways as a main cause of long-term cardiac disease and support early therapeutic management of Takotsubo.


Assuntos
Modelos Animais de Doenças , Coração , Estresse Psicológico , Cardiomiopatia de Takotsubo , Humanos , Feminino , Animais , Ratos , Cardiomiopatia de Takotsubo/metabolismo , Cardiomiopatia de Takotsubo/patologia , Ratos Wistar , Coração/fisiopatologia , Miócitos Cardíacos/metabolismo , Miócitos Cardíacos/patologia , Glucose-6-Fosfato/metabolismo , Glicólise , Estresse Psicológico/complicações
20.
J Inorg Biochem ; 245: 112257, 2023 08.
Artigo em Inglês | MEDLINE | ID: mdl-37229820

RESUMO

Kinetic and structural investigations of the flavohemoglobin-type NO dioxygenase have suggested critical roles for transient Fe(III)O2 complex formation and O2-forced movements affecting hydride transfer to the FAD cofactor and electron-transfer to the Fe(III)O2 complex. Stark-effect theory together with structural models and dipole and internal electrostatic field determinations provided a semi-quantitative spectroscopic method for investigating the proposed Fe(III)O2 complex and O2-forced movements. Deoxygenation of the enzyme causes Stark effects on the ferric heme Soret and charge-transfer bands revealing the Fe(III)O2 complex. Deoxygenation also elicits Stark effects on the FAD that expose forces and motions that create a more restricted NADH access to FAD for hydride transfer and switch electron-transfer off. Glucose also forces the enzyme toward an off state. Amino acid substitutions at the B10, E7, E11, G8, D5, and F7 positions influence the Stark effects of O2 on resting heme spin states and FAD consistent with the proposed roles of the side chains in the enzyme mechanism. Deoxygenation of ferric myoglobin and hemoglobin A also induces Stark effects on the hemes suggesting a common 'oxy-met' state. The ferric myoglobin and hemoglobin heme spectra are also glucose-responsive. A conserved glucose or glucose-6-phosphate binding site is found bridging the BC-corner and G-helix in flavohemoglobin and myoglobin suggesting novel allosteric effector roles for glucose or glucose-6-phosphate in the NO dioxygenase and O2 storage functions. The results support the proposed roles of a ferric O2 intermediate and protein motions in regulating electron-transfer during NO dioxygenase turnover.


Assuntos
Ferro , Mioglobina , Ferro/química , Mioglobina/química , Oxigênio/química , Elétrons , Glucose-6-Fosfato , Heme/química , Óxido Nítrico/metabolismo
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