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1.
BMC Neurol ; 22(1): 133, 2022 Apr 08.
Artigo em Inglês | MEDLINE | ID: mdl-35395738

RESUMO

BACKGROUND: Diabetic striatopathy is a rare neurological manifestation of nonketotic hyperglycemia that presents with contralateral hemichorea-hemiballismus. Presentation with concurrent seizures is rarely reported. CLINICAL PRESENTATION: We report a case of diabetic striatopathy presenting with focal and generalized tonic-clonic seizures (GTCS) with right hemichorea-hemiballismus induced by a ketotic hyperglycemic state. Head MRI showed high T1-weighted signal intensity in the left lentiform nucleus with no significant diffusion restriction or postcontrast enhancement. The patient's condition gradually improved, with seizure control on AEDs. Hemichorea-hemiballismus significantly improved with adequate blood sugar control and resolved with low-dose haloperidol. CONCLUSIONS: Diabetic striatopathy presenting with hemichorea-hemiballismus and concurrent GTCS has been reported previously in two cases; however, it has never been reported in ketotic hyperglycemia. To the best of our knowledge, we herein report the first case report of focal and generalized seizures in a ketotic hyperglycemic state and mesial temporal sclerosis.


Assuntos
Coreia , Diabetes Mellitus , Discinesias , Hiperglicemia , Coreia/diagnóstico por imagem , Coreia/tratamento farmacológico , Coreia/etiologia , Discinesias/etiologia , Humanos , Hiperglicemia/complicações , Cetoses , Convulsões/complicações
2.
J Dairy Sci ; 105(1): 761-771, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34635355

RESUMO

Ketosis in dairy cows often occurs in the peripartal period and is accompanied by immune dysfunction. High concentrations of ß-hydroxybutyrate (BHB) in peripheral blood during ketosis are closely related to the impairment of polymorphonuclear neutrophil (PMN) chemotaxis and contribute to immune dysfunction. The specific effect of BHB on PMN chemotaxis in dairy cows and the underlying molecular mechanisms are unclear. Here, 30 multiparous cows (within 3 wk postpartum) classified based on serum BHB as control (n = 15, BHB <0.6 mM) or clinically ketotic (n = 15, BHB >3.0 mM) were used. Blood samples were collected before feeding, and the isolated PMN were treated with platelet-activating factor for 0.5 h to activate their migration. Scanning electron microscopy revealed a longer tail in PMN of ketotic cows. In addition, the phosphorylation and transcription levels of myosin light chain 2 (MLC2) increased in PMN of ketotic cows. Polymorphonuclear neutrophils from control dairy cows were incubated with 3.0 mM BHB for different times in vitro, and 6 h was selected as the proper duration of BHB stimulation according to its inhibition effect on PMN migration using an under-agarose PMN chemotaxis model. Similarly, BHB stimulation in vitro resulted in inhibition of migration distance and deviation of migration direction of PMN, as well as a longer tail in morphology in the scanning electron microscope data, suggesting that BHB-induced PMN migration inhibition may be mediated by impairing the trailing edge contraction. To confirm this hypothesis, sotrastaurin (Sotra)-a specific inhibitor of protein kinase C (PKC), which is the core regulator of cell contraction-was used with or without BHB treatment in vitro. Sotra was pretreated 0.5 h before BHB treatment. Accordingly, BHB treatment increased the phosphorylation level of PKC and MLC2, the protein abundance of RhoA and rho-kinase 1 (ROCK1), and the mRNA abundance of PRKCA, MYL2, RHOA, and ROCK1 in PMN. In contrast, these effects of BHB on PMN were dampened by Sotra. As demonstrated by immunofluorescence experiments in vitro, the BHB-induced inhibition of trailing edge contraction of PMN was relieved by Sotra. In addition, Sotra also dampened the effects of BHB on PMN migration in vitro. Furthermore, as verified by in vivo experiments, compared with the control cows, both abundance and activation of PKC signaling were enhanced in PMN of ketotic cows. Overall, the present study revealed that high concentrations of blood BHB impaired PMN migration distance through inhibition of the trailing edge contraction, mediated by enhancing the activation of PKC-MLC2 signaling. These findings help explain the dysfunctional immune state in ketotic cows and provide information on the pathogenesis of infectious diseases secondary to ketosis.


Assuntos
Doenças dos Bovinos , Cetose , Ácido 3-Hidroxibutírico , Animais , Miosinas Cardíacas , Bovinos , Feminino , Cetoses , Cetose/veterinária , Lactação , Cadeias Leves de Miosina , Neutrófilos , Proteína Quinase C , Transdução de Sinais
3.
Open Vet J ; 11(2): 228-237, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34307080

RESUMO

Background: Ketosis is one of the most critical metabolic disorders that occur in dairy cows after parturition due to negative energy balance around calving. Aim: The study evaluated a specific therapeutic regimen of ketosis in Holstein dairy cattle by using the combination therapy including hormones, corticosteroids, propylene glycol, and vitamin B12 as well as the use of milk yield rates, insulin, insulin sensitivity, and abomasal functions monitors as diagnostic biomarkers for the recovery of ketotic cows either pre-therapy (0 days) or post-therapy (7 and 14 days). Methods: This study was conducted on ketotic cattle (n = 20) belonged to different dairy farms in Cairo and Giza governorates, Egypt. The diseased cows were undergoing clinical and biochemical investigations for the estimation of serum insulin. Quantitative Insulin Sensitivity Check Index (RQUICKI) and abomasal functions monitor mainly serum levels of gastrin, pepsinogen, and chloride. Results: The milk production rates, cost: benefit analysis ratio, and benefit of the dairy farm in ketotic animals were significantly increased post-treatment. An improvement of insulin sensitivity was stated as serum insulin, and RQUICKI were remarkably increased in post-therapeutic ketotic cows. Monitors of the abomasal function revealed abomasal functions improvement through the significant elevation of blood gastrin and a substantial reduction in serum pepsinogen due to treatment. Conclusion: The study revealed high efficacy of the applied therapeutic strategy regime. It led to a high recovery rate and a very low relapse rate for ketosis. An improvement in milk yield rates, insulin sensitivity, and abomasal function monitors was reported. Hypoinsulinaemia was still reported, however, serum insulin was improved.


Assuntos
Doenças dos Bovinos , Resistência à Insulina , Cetose , Ácido 3-Hidroxibutírico , Animais , Bovinos , Doenças dos Bovinos/tratamento farmacológico , Feminino , Insulina , Cetoses , Cetose/tratamento farmacológico , Cetose/veterinária , Lactação , Leite
4.
J Dairy Sci ; 104(8): 9130-9141, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-34001360

RESUMO

Disruption of endoplasmic reticulum (ER) homeostasis, a condition termed "ER stress," contributes to the development of liver injury in nonruminants. Because liver injury is a prominent pathological feature associated with overproduction of ketone bodies in dairy cows with ketosis, understanding the ER stress state and its functional consequences on liver injury is of particular interest. Here, 30 multiparous cows (within 3 wk postpartum) classified based on blood ß-hydroxybutyrate (BHB) as healthy (n = 15, BHB <0.6 mM) or clinically ketotic (n = 15, BHB >3.0 mM) were used. Compared with healthy cows, ketotic cows had greater levels of serum fatty acids and activities of serum aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, γ-glutamyl transferase, and glutamate dehydrogenase but lower serum glucose. Furthermore, dairy cows with ketosis had greater protein abundance of ER stress markers in liver tissue, including protein kinase RNA-like ER kinase (PERK), inositol-requiring protein-1α (IRE1α), and cleaved activating transcription factor-6 (ATF6). Cows with ketosis also had higher mRNA levels of hepatic 78-kDa glucose-regulated protein (GRP78) and spliced X-box binding protein 1 (sXBP1). These data confirmed an enhanced ER stress state in clinically ketotic cows. To explore whether enhanced hepatic ER stress was induced by elevated ketone bodies and the possible contribution of ER stress to liver injury, in vitro experiments were then performed using isolated primary calf hepatocytes treated with incremental concentrations of BHB (0, 0.6, 1.2, 3.0, and 4.8 mM) for 12 h with or without overexpression of GRP78 (the master regulator of unfolded protein response). Phosphorylation levels of PERK and IRE1α proteins, level of cleaved ATF6 protein, and mRNA abundance of GRP78 and sXBP1 in hepatocytes increased after treatment with high (3.0 and 4.8 mM) BHB, indicating a mechanistic link between excessive BHB and enhanced hepatic ER stress. Furthermore, treatment with 3.0 and 4.8 mM BHB markedly elevated activities of aspartate aminotransferase and alanine aminotransferase in cell supernatant, indicating exacerbated hepatocyte damage after ER stress was enhanced. Overexpression of GRP78 attenuated both BHB-induced ER stress and the ensuing cellular damage, suggesting that hepatocyte damage caused by excessive BHB can be mediated via enhanced ER stress. Overall, the present study revealed that ER stress may exacerbate liver injury development in clinically ketotic cows, underscoring the biological relevance of this pathway in the context of liver injury.


Assuntos
Doenças dos Bovinos , Cetose , Ácido 3-Hidroxibutírico , Animais , Bovinos , Retículo Endoplasmático , Estresse do Retículo Endoplasmático , Endorribonucleases , Feminino , Homeostase , Cetoses , Cetose/veterinária , Fígado
6.
Appl Biochem Biotechnol ; 193(3): 743-760, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33188507

RESUMO

Biocatalysis using molecular oxygen as the electron acceptor has significant potential for selective oxidations at low cost. However, oxygen is poorly soluble in water, and its slow rate of mass transfer in the aqueous phase is a major obstacle, even for laboratory-scale syntheses. Oxygen transfer can be accelerated by vigorous mechanical methods, but these are often incompatible with biological catalysts. Gentler conditions can be achieved with shallow, high surface area bag reactors that are designed for single use and generally for specialized cell culture applications. As a less-expensive alternative to these high-end bioreactors, we describe repurposing inflatable shipping pillows with resealable valves to provide high surface area mixing under oxygen for preparative synthesis of glucosone (D-arabino-hexos-2-ulose) from D-glucose using non-growing Escherichia coli whole cells containing recombinant pyranose 2-oxidase (POX) as catalyst. Parallel reactions permitted systematic study of the effects of headspace composition (i.e., air vs 100% oxygen), cell density, exogenous catalase, and reaction volume in the oxidation of 10% glucose. Importantly, only a single charge of 100% oxygen is required for stoichiometric conversion on a multi-gram scale in 18 h with resting cells, and the conversion was successfully repeated with recycled cells.


Assuntos
Reatores Biológicos , Escherichia coli/metabolismo , Cetoses/biossíntese , Oxigênio/metabolismo , Embalagem de Produtos , Catálise
7.
Biochim Biophys Acta Gen Subj ; 1865(1): 129740, 2021 01.
Artigo em Inglês | MEDLINE | ID: mdl-32956752

RESUMO

BACKGROUND: In acetic acid bacteria such as Gluconobacter oxydans or Gluconobacter cerinus, pyrroloquinoline quinone (PQQ) in the periplasm serves as the redox cofactor for several membrane-bound dehydrogenases that oxidize polyhydric alcohols to rare sugars, which can be used as a healthy alternative for traditional sugars and sweeteners. These oxidation reactions obey the generally accepted Bertrand Hudson's rule, in which only the polyhydric alcohols that possess cis d-erythro hydroxyl groups can be oxidized to 2-ketoses using PQQ as a cofactor, while the polyhydric alcohols excluding cis d-erythro hydroxyl groups ruled out oxidation by PQQ-dependent membrane-bound dehydrogenases. METHODS: Membrane fractions of G. oxydans were prepared and used as a cell-free catalyst to oxidize galactitol, with or without PQQ as a cofactor. RESULTS: In this study, we reported an interesting oxidation reaction that the polyhydric alcohols galactitol (dulcitol), which do not possess cis d-erythro hydroxyl groups, can be oxidized by PQQ-dependent membrane-bound dehydrogenase(s) of acetic acid bacteria at the C-3 and C-5 hydroxyl groups to produce rare sugars l-xylo-3-hexulose and d-tagatose. CONCLUSIONS: This reaction may represent an exception to Bertrand Hudson's rule. GENERAL SIGNIFICANCE: Bertrand Hudson's rule is a well-known theory in polyhydric alcohols oxidation by PQQ-dependent membrane-bound dehydrogenase in acetic acid bacteria. In this study, galactitol oxidation by a PQQ-dependent membrane-bound dehydrogenase represents an exception to the Bertrand Hudson's rule. Further identification of the associated enzymes and deciphering the explicit enzymatic mechanism will prove this theory.


Assuntos
Ácido Acético/metabolismo , Galactitol/metabolismo , Gluconobacter/metabolismo , Hexoses/metabolismo , Cetoses/metabolismo , Proteínas de Bactérias/metabolismo , Gluconobacter/enzimologia , Oxirredução , Oxirredutases/metabolismo , Cofator PQQ/metabolismo
8.
Neuro Endocrinol Lett ; 41(4): 162-165, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-33307650

RESUMO

INTRODUCTION: Diabetic striatopathy is a rare condition characterized by unilateral hemichorea and/or hemiballismus in the settings of uncontrolled nonketotic diabetes mellitus. Imaging studies usually reveal striatal abnormality - subtle hyperdensity on CT and T1 hyperintensity on MRI. The resolution of clinical symptoms is prompt when optimal glycaemic control is achieved. CASE REPORT: We present the case of a 90-year-old male who came to our attention for acute involuntary choreiform movements of his left-sided extremities lasting two-weeks. Apart from that neurological examination was unremarkable. His medical history included hypertension, atrial fibrillation, previous stroke with no residual disability and poorly controlled type 2 diabetes mellitus on metformin treatment. There was no history of movement disorders or exposure to neuroleptics. His glucose level on admission was 512.6 mg/dL, glycated hemoglobin was 14%. CT scan of the head demonstrated an abnormally increased intensity within the right striatum. Treatment consisted of symptomatic treatment of chorea and improvement of blood glucose control. Tiapride was started with a dose of 100 mg 4 times a day. The patient was initiated on intensive insulin therapy which included insulin glargine 10 units every evening and 12 units of insulin glulisine 3 times a day with meals. Abnormal movements resolved after normoglycemia was achieved approximately 7 days after admission. Though striatal hyperdensity was still present at follow-up CT scan after 10 days, it was less pronounced. CONCLUSION: Diabetic striatopathy is a rare but treatable disorder and should be considered in patients with poorly controlled diabetes who present with hemichorea.


Assuntos
Coreia , Diabetes Mellitus Tipo 2 , Hiperglicemia , Acidente Vascular Cerebral , Idoso de 80 Anos ou mais , Coreia/diagnóstico por imagem , Coreia/tratamento farmacológico , Humanos , Hiperglicemia/complicações , Hiperglicemia/tratamento farmacológico , Cetoses , Imageamento por Ressonância Magnética , Masculino , Pirazóis , Piridonas
9.
J Agric Food Chem ; 68(5): 1347-1353, 2020 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-31961681

RESUMO

A facile approach is introduced here for the synthesis of rare ketoses from glycerol and d-/l-glyceraldehyde (d-/l-GA). The reactions were carried out in a one-pot multienzyme fashion in which the only carbon source is glycerol. In the enzymatic cascade, glycerol is phosphorylated and then oxidized at C2 to afford dihydroxyacetone phosphate (DHAP), the key donor for enzymatic aldol reaction. Meanwhile, the primary alcohol of glycerol is also oxidized to give the acceptor molecule GA in situ (d- or l-isomer could be formed stereospecifically with either alditol oxidase or horse liver alcohol dehydrogenase). Different DHAP-dependent aldolases were used to generate the aldol adducts (rare ketohexose phosphates) with various stereoconfigurations and diastereomeric ratios. It is worth noting that the enzyme that catalyzes the phosphorylation reaction in the first step could also help recycle the phosphate in the last step to provide free rare sugar molecules. This study provides a useful method for rare ketose synthesis on a 100 mg to g scale, starting from relatively inexpensive materials which solved the problem of supplying both glycerol 3-phosphate and GA in our previous work. It also demonstrates an example of green synthesis due to highly efficient carbon usage and recycling of cofactors.


Assuntos
Álcool Desidrogenase/química , Aldeído Liases/química , Glicerol/química , Cetoses/química , Animais , Biocatálise , Fosfato de Di-Hidroxiacetona/química , Cavalos , Fosforilação
10.
Enzyme Microb Technol ; 133: 109456, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31874684

RESUMO

Dihydroxyacetone phosphate (DHAP)-dependent aldolases demonstrate important values in the production of rare ketoses due to their unique stereoselectivities. As a specific example, we developed an efficient Escherichia coli whole-cell biocatalytic cascade system in which rare ketoses were produced from abundant glycerol and catalyzed by four enzymes based on L-rhamnulose-1-phosphate aldolase (RhaD). For the semicontinuous bioconversion in which D-glyceraldehyde was continuously added, once D-glyceraldehyde was consumed, the final yields of D-sorbose and D-psicose were 15.30 g/L and 6.35 g/L, respectively. Moreover, the maximum conversion rate and productivity of D-sorbose and D-psicose were 99% and 1.11 g/L/h at 8 h, respectively. When L-glyceraldehyde was used instead of the D-isomer, the final yield of L-fructose was 16.80 g/L. Furthermore, the maximum conversion rate and productivity of L-fructose were 95% and 1.08 g/L/h at 8 h, respectively. This synthetic platform was also compatible with other various aldehydes, which allowed the production of many other high-value chemicals from glycerol.


Assuntos
Aldeído Liases/metabolismo , Escherichia coli/metabolismo , Cetoses/biossíntese , Biocatálise , Biotransformação , Frutose/metabolismo , Gliceraldeído/metabolismo , Glicerol/metabolismo , Microbiologia Industrial , Sorbose/metabolismo , Especificidade por Substrato
11.
Food Chem ; 305: 125504, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31606691

RESUMO

Glucosamine (GlcN) and GlcN-myoglobin reaction systems were incubated at 4 °C to verify that GlcN can go through non-enzymatic browning at this low temperature, and to test the hypothesis that certain reductones from GlcN non-enzymatic browning can promote the formation of deoxy- and oxymyoglobin from metmyoglobin reduction. Remarkably, alpha-dicarbonyls and self-condensation products, fructosazine and deoxyfructosazine, were produced at this relatively low temperature. The presence of myoglobin shifted GlcN non-enzymatic browning toward the formation of glucosone and fructosazine. When glucosone (250-2000 mg/L) was incubated with myoglobin it contributed to the formation of deoxymyoglobin, indicating its capacity to reduce metmyoglobin. This study opens the possibility of using GlcN in meat products to increase oxy- and deoxymyoglobin and enhance the color of meat.


Assuntos
Temperatura Baixa , Glucosamina/química , Cetoses/química , Reação de Maillard , Metamioglobina/química , Mioglobina/química , Animais , Cor , Oxirredução
12.
Anal Bioanal Chem ; 411(30): 7967-7979, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31754770

RESUMO

Naturally occurring fructosamines are of high clinical significance due to their potential use in diabetes mellitus monitoring (quantification of fructosylated hemoglobin, HbA1c) or for the investigation of their reactivity in consecutive reactions and harmfulness towards the organism. Here we report the specific synthesis of the fructosylated dipeptide L-valyl-L-histidine (Fru-Val-His) and fructosylated L-valine (Fru-Val). Both are basic tools for the development and validation of enzymatic HbA1c assays. The two fructosamine derivatives were synthesized via a protected glucosone intermediate which was coupled to the primary amine of Val or Val-His, performing a reductive amination reaction. Overall yields starting from fructose were 36% and 34% for Fru-Val and Fru-Val-His, respectively. Both compounds were achieved in purities > 90%. A HILIC-ESI-MS/MS method was developed for routine analysis of the synthesized fructosamines, including starting materials and intermediates. The presented method provides a well-defined and efficient synthesis protocol with purification steps and characterization of the desired products. The functionality of the fructosylated dipeptide has been thoroughly tested in an enzymatic HbA1c assay, showing its concentration-dependent oxidative degradation by fructosyl-peptide oxidases (FPOX). Graphical abstract.


Assuntos
Diabetes Mellitus/diagnóstico , Frutose/química , Hemoglobina A Glicada/análise , Histidina/química , Cetoses/química , Espectrometria de Massas por Ionização por Electrospray/métodos , Espectrometria de Massas em Tandem/métodos , Valina/química , Ensaios Enzimáticos , Humanos
13.
J Agric Food Chem ; 67(32): 8994-9001, 2019 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-31347366

RESUMO

The effect of simultaneous dehydration-reaction (SDR) on Amadori rearrangement product (ARP) N-(1-deoxy-d-xylulos-1-yl)-glutathione and its key degradation products, 3-deoxyxylosone (3-DX) and 1-deoxyxylosone (1-DX), were investigated in an aqueous glutathione-xylose (GSH-Xyl) system. The yield of ARP was increased to 67.98% by SDR compared with 8.44% by atmospheric thermal reaction at 80 °C. Reaction kinetics was applied to analyze the mechanism and characteristics of ARP formation and degradation under SDR. ARP formation and degradation rate was highly dependent on temperature, and the latter was more sensitive to temperature. By regulating the reaction conditions of temperature and pH, the ratio of ARP formation rate constant to its degradation rate constant could be controlled to achieve an efficient preparation of ARP from GSH-Xyl Maillard reaction through SDR.


Assuntos
Glutationa/química , Xilose/química , Concentração de Íons de Hidrogênio , Cetoses/química , Cinética , Reação de Maillard , Temperatura
14.
J Antibiot (Tokyo) ; 72(6): 420-431, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-30903099

RESUMO

Fusobacterium nucleatum is an oral bacteria related to various types of diseases. As Gram-negative bacteria, lipopolysaccharide (LPS) of Fusobacterium nucleatum could be a potential virulence factor. Recently, the structure of O-antigen in LPS of Fusobacterium nucleatum strain 25586 was elucidated to contain a trisaccharide repeating unit -(4-ß-Nonp5Am-4-α-L-6dAltpNAc3PCho-3-ß-D-QuipNAc)-. The nonulosonic acid characterized as 5-acetamidino-3,5,9-trideoxy-L-glycero-L-gluco-non-2-ulosonic acid (named as fusaminic acid), and 2-acetamido-2,6-dideoxy-L-altrose are the novel monosaccharides isolated. Herein we report the de novo synthesis of 5-N-acetyl fusaminic acid and the thioglycoside derivative in order to further investigate the biological significance of nonulosonic acids for bacterial pathogenesis.


Assuntos
Bactérias/química , Fusobacterium nucleatum/química , Cetoses/síntese química , Monossacarídeos/síntese química , Configuração de Carboidratos , Cetoses/química , Monossacarídeos/química
16.
Carbohydr Res ; 474: 8-15, 2019 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-30665025

RESUMO

The article is devoted to the problem of molecular modeling of tautomeric and epimeric equilibria in aqueous solutions of unfunctionalized d-aldo- and d-ketohexoses. We have applied the computational protocol proposed in our previous article [Gaweda, Plazinski, Phys. Chem. Chem. Phys., 2017, 19, 20760-20772, doi:10.1039/c7cp02920a], originally designed to study the conformational features of saccharides, in order to check whether it can be extended to the case of tautomeric/epimeric equilibria of monosaccharides. The results show that the most important trends are correctly reflected in a qualitative manner, i.e. within the limits of 'chemical accuracy' (∼±4 kJ/mol). Insight into the calculated conformational energies provides a molecular interpretation of the tautomeric preferences of aldohexoses, according to which the pyranose/furanose ratio is determined mainly by the energy level of pyranose forms, whereas the energies of furanose forms are approximately constant along the series. The investigated paths of epimerization suggest that epimerization of aldohexopyranoses at any center favors the equatorial arrangements of the hydroxyl group. The energetic effects of epimerization in furanoses are significantly lower and do not exhibit related systematic trends.


Assuntos
Hexoses/química , Cetoses/química , Simulação de Dinâmica Molecular , Configuração de Carboidratos , Cinética , Teoria Quântica , Estereoisomerismo , Termodinâmica , Água/química
17.
J Colloid Interface Sci ; 541: 75-85, 2019 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-30684752

RESUMO

Nanomaterials possessing enzyme-like activity have been extensively studied owing to their high stability and tunable catalytic properties. In this work, a simple method has been developed for the synthesis of porous manganese oxide/manganese ferrite (MnOx/MnFe2O4) nanopopcorns (MFNPs) in neutral media. The MFNPs exhibit dual enzymatic activities towards selective oxidation of ketoses followed by H2O2-induced decline of its catalytic activity. MFNPs, with MnFe2O4 as the core material and an outer layer rich in MnOx, were synthesized from ammonium iron(III) citrate and potassium permanganate at 70 °C for 12 h followed by annealing at 300 °C for 6 h. The nanozyme, MFNPs, exhibited oxidase-like activity, which was proved by the oxidation of amplex red (AR) in the presence of dissolved oxygen in the solution, to form fluorescent resorufin. The activity of MFNPs is highly suppressed by H2O2 as a result of its induced dissolution of MnOx. In addition, MFNPs having catalytic activity towards the selective oxidation of ketoses (e.g., fructose) followed by the formation of H2O2. The as-formed H2O2 diminished the catalytic activity of MFNPs for the AR oxidation to form fluorescent resorufin. Upon increasing fructose concentration, the fluorescence of resorufin decreases. Since the MFNPs do not show catalytic activity towards aldose sugars, such as glucose, sucrose, and mannose, the AR/MFNPs probe has high selectivity and sensitivity for detection of fructose with a limit of detection of 32 µM. Our study shows its great potential for quantitation of fructose in honey samples.


Assuntos
Materiais Biomiméticos/química , Compostos Férricos/química , Cetoses/análise , Compostos de Manganês/química , Nanoestruturas/química , Óxidos/química , Peroxidase/metabolismo , Peróxido de Hidrogênio/farmacologia , Oxidantes/farmacologia
18.
Curr Opin Chem Biol ; 49: 113-121, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-30580186

RESUMO

In 2014, the first fungal pyrroloquinoline-quinone (PQQ)-dependent enzyme was discovered as a pyranose dehydrogenase from the basidiomycete Coprinopsis cinerea (CcPDH). This discovery laid the foundation for a new Auxiliary Activities (AA) family, AA12, in the Carbohydrate-Active enZymes (CAZy) database and revealed a novel enzymatic activity potentially involved in biomass conversion. This review summarizes recent progress made in research on this fungal oxidoreductase and related enzymes. CcPDH consists of the catalytic PQQ-binding AA12 domain, an N-terminal cytochrome b AA8 domain, and a C-terminal family 1 carbohydrate-binding module (CBM1). CcPDH oxidizes 2-keto-d-glucose (d-glucosone), l-fucose, and rare sugars such as d-arabinose and l-galactose, and can activate lytic polysaccharide monooxygenases (LPMOs). Bioinformatic studies suggest a widespread occurrence of quinoproteins in eukaryotes as well as prokaryotes.


Assuntos
Basidiomycota/enzimologia , Biocatálise , Oxirredutases/metabolismo , Cofator PQQ/metabolismo , Arabinose/metabolismo , Fucose/metabolismo , Galactose/metabolismo , Cetoses/metabolismo , Oxirredução , Especificidade por Substrato
19.
Metab Eng ; 52: 243-252, 2019 03.
Artigo em Inglês | MEDLINE | ID: mdl-30578862

RESUMO

The high-value ketocarotenoid astaxanthin, a natural red colorant with powerful antioxidant activity, is synthesised from ß-carotene by a hydroxylase and an oxygenase enzyme, which perform the addition of two hydroxyl and keto moieties, respectively. Several routes of intermediates, depending on the sequence of action of these enzymes, lead to the formation of astaxanthin. In the present study, the enzyme activities of 3, 3' ß-carotene hydroxylase (CRTZ) and 4, 4' ß-carotene oxygenase (CRTW) have been combined through the creation of "new to nature" enzyme fusions in order to overcome leakage of non-endogenous intermediates and pleotropic effects associated with their high levels in plants. The utility of flexible linker sequences of varying size has been assessed in the construction of pZ-W enzyme fusions. Frist, in vivo color complementation assays in Escherichia coli have been used to evaluate the potential of the fusion enzymes. Analysis of the carotenoid pigments present in strains generated indicated that the enzyme fusions only possess both catalytic activities when CRTZ is attached as the N-terminal module. Astaxanthin levels in E. coli cells were increased by 1.4-fold when the CRTZ and CRTW enzymes were fused compared to the individual enzymes. Transient expression in Nicotiana benthamiana was then performed in order to assess the potential of the fusions in a plant system. The production of valuable ketocarotenoids was achieved using this plant-based transient expression system. This revealed that CRTZ and CRTW, transiently expressed as a fusion, accumulated similar levels of astaxanthin compared to the expression of the individual enzymes whilst being associated with reduced ketocarotenoid intermediate levels (e.g. phoenicoxanthin, canthaxanthin and 3-OH-echinenone) and a reduced rate of leaf senescence after transformation. Therefore, the quality of the plant material producing the ketocarotenoids was enhanced due to a reduction in the stress induced by the accumulation of high levels of heterologous ketocarotenoid intermediates. The size of the linkers appeared to have no effect upon activity. The potential of the approach to production of valuable plant derived products is discussed.


Assuntos
Carotenoides/biossíntese , Cetoses/biossíntese , Plantas/enzimologia , Escherichia coli/genética , Escherichia coli/metabolismo , Fusão Gênica , Engenharia Metabólica/métodos , Oxigenases de Função Mista/genética , Oxigenases de Função Mista/metabolismo , Folhas de Planta/metabolismo , Plantas/genética , Plantas Geneticamente Modificadas , Plasmídeos/genética , Tabaco/genética , Tabaco/metabolismo , Xantofilas/biossíntese
20.
Folia Biol (Praha) ; 65(4): 195-202, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31903893

RESUMO

A side effect of diabetes is formation of glycated proteins and, from them, production of advanced early glycation end products that could determine aberrant immune responses at the systemic level. We investigated a relevant aberrant post-translational modification (PTM) in diabetes based on synthetic peptides modified on the lysine side chain residues with 1-deoxyfructopyranosyl moiety as a possible modification related to glycation. The PTM peptides were used as molecular probes for detection of possible specific autoantibodies developed by diabetic patients. The PDC-E2(167-186) sequence from the pyruvate dehydrogenase complex was selected and tested as a candidate peptide for antibody detection. The structure-based designed type I' ß-turn CSF114 peptide was also used as a synthetic scaffold. Twenty-seven consecutive type 1 diabetic patients and 29 healthy controls were recruited for the study. In principle, the 'chemical reverse approach', based on the use of patient sera to screen the synthetic modified peptides, leads to the identification of specific probes able to characterize highly specific autoantibodies as disease biomarkers of autoimmune disorders. Quite surprisingly, both peptides modified with the (1-deoxyfructosyl)-lysine did not lead to significant results. Both IgG and IgM differences between the two populations were not significant. These data can be rationalized considering that i) IgGs in diabetic subjects exhibit a high degree of glycation, leading to decreased functionality; ii) IgGs in diabetic subjects exhibit a privileged response vs proteins containing advanced glycation products (e.g., methylglyoxal, glyoxal, glucosone, hydroimidazolone, dihydroxyimidazolidine) and only a minor one with respect to (1-deoxyfructosyl)-lysine.


Assuntos
Peptídeos/química , Peptídeos/metabolismo , Diabetes Mellitus Tipo 1/metabolismo , Produtos Finais de Glicação Avançada/metabolismo , Glicosilação , Glioxal/metabolismo , Humanos , Imidazóis/metabolismo , Imunoensaio , Cetoses/metabolismo , Lisina/química , Lisina/metabolismo , Processamento de Proteína Pós-Traducional , Aldeído Pirúvico/metabolismo
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