Legume-wide comparative analysis of pod shatter locus PDH1 reveals phaseoloid specificity, high cowpea expression, and stress responsive genomic context.

Pod dehiscence is a major source of yield loss in legumes, which is exacerbated by aridity. Disruptive mutations in "Pod indehiscent 1" (PDH1), a pod sclerenchyma-specific lignin biosynthesis gene, has been linked to significant reductions in dehiscence in several legume species. We compared syntenic PDH1 regions across 12 legumes and two outgroups to uncover key historical evolutionary trends at this important locus. Our results clarified the extent to which PDH1 orthologs are present in legumes, showing the typical genomic context surrounding PDH1 has only arisen relatively recently in certain phaseoloid species (Vigna, Phaseolus, Glycine). The notable absence of PDH1 in Cajanus cajan may be a major contributor to its indehiscent phenotype compared with other phaseoloids. In addition, we identified a novel PDH1 ortholog in Vigna angularis and detected remarkable increases in PDH1 transcript abundance during Vigna unguiculata pod development. Investigation of the shared genomic context of PDH1 revealed it lies in a hotspot of transcription factors and signaling gene families that respond to abscisic acid and drought stress, which we hypothesize may be an additional factor influencing expression of PDH1 under specific environmental conditions. Our findings provide key insights into the evolutionary history of PDH1 and lay the foundation for optimizing the pod dehiscence role of PDH1 in major and understudied legume species.

Metabolic priming in G6PDH isoenzyme-replaced tobacco lines improves stress tolerance and seed yields via altering assimilate partitioning.

We investigated the basis for better performance of transgenic Nicotiana tabacum plants with G6PDH-isoenzyme replacement in the cytosol (Xanthi::cP2::cytRNAi, Scharte et al., 2009). After six generations of selfing, infiltration of Phytophthora nicotianae zoospores into source leaves confirmed that defence responses (ROS, callose) are accelerated, showing as fast cell death of the infected tissue. Yet, stress-related hormone profiles resembled susceptible Xanthi and not resistant cultivar SNN, hinting at mainly metabolic adjustments in the transgenic lines. Leaves of non-stressed plants contained twofold elevated fructose-2,6-bisphosphate (F2,6P2 ) levels, leading to partial sugar retention (soluble sugars, starch) and elevated hexose-to-sucrose ratios, but also more lipids. Above-ground biomass lay in between susceptible Xanthi and resistant SNN, with photo-assimilates preferentially allocated to inflorescences. Seeds were heavier with higher lipid-to-carbohydrate ratios, resulting in increased harvest yields - also under water limitation. Abiotic stress tolerance (salt, drought) was improved during germination, and in floated leaf disks of non-stressed plants. In leaves of salt-watered plants, proline accumulated to higher levels during illumination, concomitant with efficient NADP(H) use and recycling. Non-stressed plants showed enhanced PSII-induction kinetics (upon dark-light transition) with little differences at the stationary phase. Leaf exudates contained 10% less sucrose, similar amino acids, but more fatty acids - especially in the light. Export of specific fatty acids via the phloem may contribute to both, earlier flowering and higher seed yields of the Xanthi-cP2 lines. Apparently, metabolic priming by F2,6P2 -combined with sustained NADP(H) turnover-bypasses the genetically fixed growth-defence trade-off, rendering tobacco plants more stress-resilient and productive.

Mitochondria-Translocated PGK1 Functions as a Protein Kinase to Coordinate Glycolysis and the TCA Cycle in Tumorigenesis.

It is unclear how the Warburg effect that exemplifies enhanced glycolysis in the cytosol is coordinated with suppressed mitochondrial pyruvate metabolism. We demonstrate here that hypoxia, EGFR activation, and expression of K-Ras G12V and B-Raf V600E induce mitochondrial translocation of phosphoglycerate kinase 1 (PGK1); this is mediated by ERK-dependent PGK1 S203 phosphorylation and subsequent PIN1-mediated cis-trans isomerization. Mitochondrial PGK1 acts as a protein kinase to phosphorylate pyruvate dehydrogenase kinase 1 (PDHK1) at T338, which activates PDHK1 to phosphorylate and inhibit the pyruvate dehydrogenase (PDH) complex. This reduces mitochondrial pyruvate utilization, suppresses reactive oxygen species production, increases lactate production, and promotes brain tumorigenesis. Furthermore, PGK1 S203 and PDHK1 T338 phosphorylation levels correlate with PDH S293 inactivating phosphorylation levels and poor prognosis in glioblastoma patients. This work highlights that PGK1 acts as a protein kinase in coordinating glycolysis and the tricarboxylic acid (TCA) cycle, which is instrumental in cancer metabolism and tumorigenesis.

The Role of Glucose-6-phosphate Dehydrogenase in the Wine Yeast Hanseniaspora uvarum.

Hanseniaspora uvarum is the predominant yeast species in the majority of wine fermentations, which has only recently become amenable to directed genetic manipulation. The genetics and metabolism of H. uvarum have been poorly studied as compared to other yeasts of biotechnological importance. This work describes the construction and characterization of homozygous deletion mutants in the HuZWF1 gene, encoding glucose-6-phosphate dehydrogenase (G6PDH), which provides the entrance into the oxidative part of the pentose phosphate pathway (PPP) and serves as a major source of NADPH for anabolic reactions and oxidative stress response. Huzwf1 deletion mutants grow more slowly on glucose medium than wild-type and are hypersensitive both to hydrogen peroxide and potassium bisulfite, indicating that G6PDH activity is required to cope with these stresses. The mutant also requires methionine for growth. Enzyme activity can be restored by the expression of heterologous G6PDH genes from other yeasts and humans under the control of a strong endogenous promoter. These findings provide the basis for a better adaptation of H. uvarum to conditions used in wine fermentations, as well as its use for other biotechnological purposes and as an expression organism for studying G6PDH functions in patients with hemolytic anemia.

The Acid Roles of PtSn@Al2O3 in the Synthesis and Performance of Propane Dehydrogenation.

In this study, a PtSn/Al2O3 catalyst with bimetallic uniform distribution in the sphere was synthesized. The PDH performance and characterization analyses, such as with FTIR, XPS, and NH3-TPD, were investigated. The effects of acid on the PDH performance were analyzed. Citric acid (CA) acted as a competing adsorbent in the preparation process of the PtSn/Al2O3 catalyst to synthesize the uniform catalyst. Water washing and alkali-treated samples were also studied. SEM line scanning revealed that increased the apparent concentration of Pt metal from 0.23 to 0.30 with citric acid. In contrast to the fresh PtSn/Al2O3 catalyst, the addition of citric acid increased the PDH selectivity from 74% to 93%. After alkali or water washing treatments, the catalyst's selectivity further increased to 96%. Strong acid sites promoted the breaking of C-C bonds during the PDH reaction, resulting in more methane and ethylene byproducts, and decreased catalyst selectivity for fresh PtSn/Al2O3. From the PDH reaction thermodynamic analysis, a relatively sub-atmospheric pressure environment with a lower propane pressure could be the reasonable choice.

Characterization of the enzymatic and multifunctional properties of Acinetobacter baumannii erythrose-4-phosphate dehydrogenase (E4PDH).

Infections due to Acinetobacter baumannii (A. baumannii) are rapidly increasing worldwide and consequently therapeutic options for treatment are limited. The emergence of multi drug resistant (MDR) strains has rendered available antibiotics ineffective, necessitating the urgent discovery of new drugs and drug targets. The vitamin B6 biosynthetic pathway has been considered as a potential antibacterial drug target but it is as yet uncharacterized for A. baumannii. In the current work, we have carried out in silico and biochemical characterization of Erythrose-4-phosphate dehydrogenase (E4PDH) (EC 1.2.1.72). This enzyme catalyzes the first step in the deoxyxylulose-5-phosphate (DXP) dependent Vitamin B6 biosynthetic pathway i.e. the conversion of d-erythrose-4-phosphate (E4P) to 4-Phosphoerythronate. E4PDH also possesses an additional activity whereby it can catalyze the conversion of Glyceraldehyde-3-phosphate (G3P) to 1,3 bisphosphoglycerate (1,3BPG). Our studies have revealed that this enzyme exhibits an alternate moonlighting function as a cell surface receptor for the human iron transport proteins transferrin (Tf) and lactoferrin (Lf). The present work reports the internalization of Tf and consequent iron acquisition as an alternate strategy for iron acquisition. Given its essential role in two crucial pathways i.e. metabolism and iron acquisition, A. baumannii E4PDH may play a vital role in bacterial pathogenesis.

Association of Phosphorylated Pyruvate Dehydrogenase with Pyruvate Kinase M2 Promotes PKM2 Stability in Response to Insulin.

Insulin is a crucial signalling molecule that primarily functions to reduce blood glucose levels through cellular uptake of glucose. In addition to its role in glucose homeostasis, insulin has been shown to regulate cell proliferation. Specifically, insulin enhances the phosphorylation of pyruvate dehydrogenase E1α (PDHA1) at the Ser293 residue and promotes the proliferation of HepG2 hepatocellular carcinoma cells. Furthermore, we previously observed that p-Ser293 PDHA1 bound with pyruvate kinase M2 (PKM2) as confirmed by coimmunoprecipitation. In this study, we used an in silico analysis to predict the structural conformation of the two binding proteins. However, the function of the protein complex remained unclear. To investigate further, we treated cells with si-PDHA1 and si-PKM2, which led to a reduction in PKM2 and p-Ser293 PDHA1 levels, respectively. Additionally, we found that the PDHA S293A dephospho-mimic reduced PKM2 levels and its associated enzyme activity. Treatment with MG132 and leupeptin impeded the PDHA1 S293A-mediated PKM2 reduction. These results suggest that the association between p-PDHA1 and PKM2 promotes their stability and protects them from protein degradation. Of interest, we observed that p-PDHA1 and PKM2 were localized in the nucleus in liver cancer patients. Under insulin stimulation, the knockdown of both PDHA1 and PKM2 led to a reduction in the expression of common genes, including KDMB1. These findings suggest that p-PDHA1 and PKM2 play a regulatory role in these proteins' expression and induce tumorigenesis in response to insulin.

An Optimized Dihydrodibenzothiazepine Lead Compound (SBI-0797750) as a Potent and Selective Inhibitor of Plasmodium falciparum and P. vivax Glucose 6-Phosphate Dehydrogenase 6-Phosphogluconolactonase.

In Plasmodium, the first two and rate-limiting enzymes of the pentose phosphate pathway, glucose 6-phosphate dehydrogenase (G6PD) and the 6-phosphogluconolactonase, are bifunctionally fused to a unique enzyme named GluPho, differing structurally and mechanistically from the respective human orthologs. Consistent with the enzyme's essentiality for malaria parasite proliferation and propagation, human G6PD deficiency has immense impact on protection against severe malaria, making PfGluPho an attractive antimalarial drug target. Herein we report on the optimized lead compound N-(((2R,4S)-1-cyclobutyl-4-hydroxypyrrolidin-2-yl)methyl)-6-fluoro-4-methyl-11-oxo-10,11-dihydrodibenzo[b,f][1,4]thiazepine-8-carboxamide (SBI-0797750), a potent and fully selective PfGluPho inhibitor with robust nanomolar activity against recombinant PfGluPho, PvG6PD, and P. falciparum blood-stage parasites. Mode-of-action studies have confirmed that SBI-0797750 disturbs the cytosolic glutathione-dependent redox potential, as well as the cytosolic and mitochondrial H2O2 homeostasis of P. falciparum blood stages, at low nanomolar concentrations. Moreover, SBI-0797750 does not harm red blood cell (RBC) integrity and phagocytosis and thus does not promote anemia. SBI-0797750 is therefore a very promising antimalarial lead compound.

Genome-wide identification and comparative evolutionary analysis of sorbitol metabolism pathway genes in four Rosaceae species and three model plants.

In contrast to most land plant species, sorbitol, instead of sucrose, is the major photosynthetic product in many Rosaceae species. It has been well illustrated that three key functional genes encoding sorbitol-6-phosphate dehydrogenase (S6PDH), sorbitol dehydrogenase (SDH), and sorbitol transporter (SOT), are mainly responsible for the synthesis, degradation and transportation of sorbitol. In this study, the genome-wide identification of S6PDH, SDH and SOT genes was conducted in four Rosaceae species, peach, mei, apple and pear, and showed the sorbitol bio-pathway to be dominant (named sorbitol present group, SPG); another three related species, including tomato, poplar and Arabidopsis, showed a non-sorbitol bio-pathway (named sorbitol absent group, SAG). To understand the evolutionary differences of the three important gene families between SAG and SPG, their corresponding gene duplication, evolutionary rate, codon bias and positive selection patterns have been analyzed and compared. The sorbitol pathway genes in SPG were found to be expanded through dispersed and tandem gene duplications. Branch-specific model analyses revealed SDH and S6PDH clade A were under stronger purifying selection in SPG. A higher frequency of optimal codons was found in S6PDH and SDH than that of SOT in SPG, confirming the purifying selection effect on them. In addition, branch-site model analyses revealed SOT genes were under positive selection in SPG. Expression analyses showed diverse expression patterns of sorbitol-related genes. Overall, these findings provide new insights in the evolutionary characteristics for the three key sorbitol metabolism-related gene families in Rosaceae and other non-sorbitol dominant pathway species.

Glucose-6-phosphate dehydrogenase promotes the infection of Chilli veinal mottle virus through affecting ROS signaling in Nicotiana benthamiana.

MAIN CONCLUSION: G6PDH negatively regulates viral accumulation in Nicotiana benthamiana through RBOHB-associated ROS signaling. Anti-oxidative metabolism and phytohormone-mediated immunity responses play important roles in virus infection. Glucose-6-phosphate dehydrogenase (G6PDH) is an enzyme in the pentose phosphate pathway, which plays an important role in maintaining intracellular redox homeostasis and has functions in plant growth, development and stress tolerance. However, the role of G6PDH in plants response to virus infection is poorly understood. In this study, NbG6PDH was found to be down-regulated after Chilli veinal mottle virus (ChiVMV-GFP) infection in Nicotiana benthamiana. Subcellular localization of NbG6PDH showed that it was punctate distributed in the protoplasm. Silencing of NbG6PDH reduced the sensitivity of N. benthamiana plants to ChiVMV-GFP. By contrast, transient overexpression of NbG6PDH promoted the accumulation of the virus. The results of physiological indexes showed that glutathione (GSH), catalase (CAT) and proline played an important role in maintaining plants physiological homeostasis. The results of gene expression detection showed that jasmonic acid/ethylene (JA/ET) signaling pathway was significantly correlated with the response of N. benthamiana to ChiVMV-GFP infection, and the changes of N. benthamiana respiratory burst oxidase homologues B (NbRBOHB) indicated that the NbG6PDH-dependent ROS may be regulated by NbRBOHB. Pretreatment of the inducer of reactive oxygen species (ROS) promoted virus infection, whereas inhibitor of ROS alleviated virus infection. Thus, our results indicate that the promoting effect of NbG6PDH on ChiVMV-GFP infection may be related to the NbRBOHB-regulated ROS production.

A CMOS Integrator-Based Clock-Free Time-to-Digital Converter for Home-Monitoring LiDAR Sensors.

This paper presents a nine-bit integrator-based time-to-digital converter (I-TDC) realized in a 180 nm CMOS technology for the applications of indoor home-monitoring light detection and ranging (LiDAR) sensors. The proposed I-TDC exploits a clock-free configuration so as to discard clock-related dynamic power consumption and some notorious issues such as skew, glitch, and synchronization. It consists of a one-dimensional (1D) flash TDC to generate coarse-control codes and an integrator with a peak detection and hold (PDH) circuit to produce fine-control codes. A thermometer-to-binary converter is added to the 1D flash TDC, yielding four-bit coarse codes so that the measured detection range can be represented by nine-bit digital codes in total. Test chips of the proposed I-TDC demonstrate the measured results of the 53 dB dynamic range, i.e., the maximum detection range of 33.6 m and the minimum range of 7.5 cm. The chip core occupies the area of 0.14 × 1.4 mm2, with the power dissipation of 1.6 mW from a single 1.2-V supply.

Genome-Wide Investigation of G6PDH Gene in Strawberry: Evolution and Expression Analysis during Development and Stress.

As one of the key enzymes in the pentose phosphate pathway (PPP), glucose-6-phosphate dehydrogenase (G6PDH) provides NADPH and plays an important role in plant development and stress responses. However, little information was available about the G6PDH genes in strawberry (Fragaria × ananassa). The recent release of the whole-genome sequence of strawberry allowed us to perform a genome-wide investigation into the organization and expression profiling of strawberry G6PDH genes. In the present study, 19 strawberry G6PDH genes (FaG6PDHs) were identified from the strawberry genome database. They were designated as FaG6PDH1 to FaG6PDH19, respectively, according to the conserved domain of each subfamily and multiple sequence alignment with Arabidopsis. According to their structural and phylogenetic features, the 19 FaG6PDHs were further classified into five types: Cy, P1, P1.1, P2 and PO. The number and location of exons and introns are similar, suggesting that genes of the same type are very similar and are alleles. A cis-element analysis inferred that FaG6PDHs possessed at least one stress-responsive cis-acting element. Expression profiles derived from transcriptome data analysis exhibited distinct expression patterns of FaG6PDHs genes in different developmental stages. Real-time quantitative PCR was used to detect the expression level of five types FaG6PDHs genes and demonstrated that the genes were expressed and responded to multiple abiotic stress and hormonal treatments.

Short-term exposure to radiofrequency radiation and metabolic enzymes' activities during pregnancy and prenatal development.

Radiofrequency radiation (RFR) as an environmental and physical pollutant may induce vulnerability to toxicity and disturb fetal development. Therefore, the potential health effects of short-term mobile phone like RFR exposure (GSM 1800 MHz; 14 V/m, 2 mW/kg specific absorption rate (SAR) during 15 min/day for a week) during pregnancy and also the development of fetuses were investigated. Hepatic glucose regulation and glutathione-dependent enzymes' capacities were biochemically analyzed in adult (female) and pregnant New Zealand White rabbits. Pregnant rabbits' two-day-old offspring were included to understand their developmental stages under short-term maternal RFR exposure. We analyzed two regulatory enzymes in the oxidative phase of phosphogluconate pathways to interpret the cytosolic NADPH's biosynthesis for maintaining mitochondrial energy metabolism. Moreover, the efficiencies of maternal glutathione-dependent enzymes on both the removal of metabolic disturbances during pregnancy and fetus development were examined. Whole-body RFR exposures were applied to pregnant animals from the 15th to the 22nd day of their gestations, i.e., the maturation periods of tissues and organs for rabbit fetuses. There were significant differences in hepatic glucose regulation and GSH-dependent enzymes' capacities with pregnancy and short-term RFR exposure. Consequently, we observed that intrauterine exposure to RFR might lead to cellular ROS- dependent disturbances in metabolic activity and any deficiency in the intracellular antioxidant (ROS-scavenging) system. This study might be a novel insight into further studies on the possible effects of short-term RF exposure and prenatal development.

Multiple Roles of Alkanethiolate-Ligands in Direct Formation of H2 O2 over Pd Nanoparticles.

Coadsorbed organic species including thiolates can promote direct synthesis of hydrogen peroxide from H2 and O2 over Pd particles. Here, density functional theory based kinetic modeling, augmented with activity measurements and vibrational spectroscopy are used to provide atomistic understanding of direct H2 O2 formation over alkylthiolate(RS) Pd. We find that the RS species are oxidized during reaction conditions yielding RSO2 as the effective ligand. The RSO2 ligand shows superior ability for proton transfer to the intermediate surface species OOH, which accelerates the formation of H2 O2 . The ligands promote the selectivity also by blocking sites for unselective water formation and by modifying the electronic structure of Pd. The work rationalizes observations of enhanced selectivity of direct H2 O2 formation over ligand-funtionalized Pd nanoparticles and shows that engineering of organic surface modifiers can be used to promote desired hydrogen transfer routes.

Deletion of Voltage-Dependent Anion Channel 1 knocks mitochondria down triggering metabolic rewiring in yeast.

The Voltage-Dependent Anion-selective Channel (VDAC) is the pore-forming protein of mitochondrial outer membrane, allowing metabolites and ions exchanges. In Saccharomyces cerevisiae, inactivation of POR1, encoding VDAC1, produces defective growth in the presence of non-fermentable carbon source. Here, we characterized the whole-genome expression pattern of a VDAC1-null strain (Δpor1) by microarray analysis, discovering that the expression of mitochondrial genes was completely abolished, as consequence of the dramatic reduction of mtDNA. To overcome organelle dysfunction, Δpor1 cells do not activate the rescue signaling retrograde response, as ρ0 cells, and rather carry out complete metabolic rewiring. The TCA cycle works in a "branched" fashion, shunting intermediates towards mitochondrial pyruvate generation via malic enzyme, and the glycolysis-derived pyruvate is pushed towards cytosolic utilization by PDH bypass rather than the canonical mitochondrial uptake. Overall, Δpor1 cells enhance phospholipid biosynthesis, accumulate lipid droplets, increase vacuoles and cell size, overproduce and excrete inositol. Such unexpected re-arrangement of whole metabolism suggests a regulatory role of VDAC1 in cell bioenergetics.

Effects of PKB/Akt inhibitors on insulin-stimulated lipogenesis and phosphorylation state of lipogenic enzymes in white adipose tissue.

We investigated acute effects of two allosteric protein kinase B (PKB) inhibitors, MK-2206 and Akti-1/2, on insulin-stimulated lipogenesis in rat epididymal adipocytes incubated with fructose as carbohydrate substrate. In parallel, the phosphorylation state of lipogenic enzymes in adipocytes and incubated epididymal fat pads was monitored by immunoblotting. Preincubation of rat epididymal adipocytes with PKB inhibitors dose-dependently inhibited the following: insulin-stimulated lipogenesis, increased PKB Ser473 phosphorylation, increased PKB activity and decreased acetyl-CoA carboxylase (ACC) Ser79 phosphorylation. In contrast, the effect of insulin to decrease the phosphorylation of pyruvate dehydrogenase (PDH) at Ser293 and Ser300 was not abolished by PKB inhibition. Insulin treatment also induced ATP-citrate lyase (ACL) Ser454 phosphorylation, but this effect was less sensitive to PKB inhibitors than ACC dephosphorylation by insulin. In incubated rat epididymal fat pads, Akti-1/2 treatment reversed insulin-induced ACC dephosphorylation, while ACL phosphorylation by insulin was maintained. ACL and ACC purified from white adipose tissue were poor substrates for PKBα in vitro. However, effects of wortmannin and torin, along with Akti-1/2 and MK-2206, on recognized PKB target phosphorylation by insulin were similar to their effects on insulin-induced ACL phosphorylation, suggesting that PKB could be the physiological kinase for ACL phosphorylation by insulin. In incubated epididymal fat pads from wild-type versus ACC1/2 S79A/S212A knockin mice, effects of insulin to increase lipogenesis from radioactive fructose or from radioactive acetate were reduced but not abolished. Together, the results support a key role for PKB in mediating insulin-stimulated lipogenesis by decreasing ACC phosphorylation, but not by decreasing PDH phosphorylation.

Functional and post-translational characterization of pyruvate dehydrogenase demonstrates repression of activity in the liver but not skeletal muscle of the Richardson's ground squirrel (Urocitellus richardsonii) during hibernation.

Hibernation consists of a series of physiological and biochemical alterations in an animal that allows for reduced body temperatures down to near ambient levels and substantial fuel conservation allowing it to survive on stored fat supplies accumulated during the summer. The Richardson's ground squirrel is one such hibernator that undergoes such changes for as long as 9 months of the year. This study examines the role of regulation of the pyruvate dehydrogenase complex (PDC) during hibernation in the skeletal muscle and liver of the Richardson's ground squirrel. The current study demonstrates a great reduction in the activity of PDC in the hibernating liver, but not in the skeletal muscle. This was matched by a significant increase in the phosphorylation on a regulatory serine residue (S300) of the pyruvate dehydrogenase (PDH) E1α subunit. Examining the expression patterns of the relevant kinases for PDH and the associated phosphatase demonstrated some unexpected results. Specifically, an increase in PDKs 1 and 2 and a decrease in PDK4 was noted in the skeletal muscle tissue in response to hibernation and no alterations in the expression patterns of any of these enzymes were noted in the liver. This suggests that alternative modes of regulation of the kinases may be at play in hibernation to bring about the observed effects. Taken together this study demonstrates that PDH regulatory responses differ markedly between tissues and emphasize the importance of inhibition of the complex in the liver during hibernation.

The specific PKC-α inhibitor chelerythrine blunts costunolide-induced eryptosis.

Costunolide, a natural sesquiterpene lactone, has multiple pharmacological activities such as neuroprotection or induction of apoptosis and eryptosis. However, the effects of costunolide on pro-survival factors and enzymes in human erythrocytes, e.g. glutathione and glucose-6-phosphate dehydrogenase (G6PDH) respectively, have not been studied yet. Our aim was to determine the mechanisms underlying costunolide-induced eryptosis and to reverse this process. Phosphatidylserine exposure was estimated from annexin-V-binding, cell volume from forward scatter in flow cytometry, and intracellular glutathione [GSH]i from high performance liquid chromatography. The oxidized status of intracellular glutathione and enzyme activities were measured by spectrophotometry. Treatment of erythrocytes with costunolide dose-dependently enhanced the percentage of annexin-V-binding cells, decreased the cell volume, depleted [GSH]i and completely inhibited G6PDH activity. The effects of costunolide on annexin-V-binding and cell volume were significantly reversed by pre-treatment of erythrocytes with the specific PKC-α inhibitor chelerythrine. The latter, however, had no effect on costunolide-induced GSH depletion. Costunolide induces eryptosis, depletes [GSH]i and inactivates G6PDH activity. Furthermore, our study reveals an inhibitory effect of chelerythrine on costunolide-induced eryptosis, indicating a relationship between costunolide and PKC-α. In addition, chelerythrine acts independently of the GSH depletion. Understanding the mechanisms of G6PDH inhibition accompanied by GSH depletion should be useful for development of anti-malarial therapeutic strategies or for synthetic lethality-based approaches to escalate oxidative stress in cancer cells for their sensitization to chemotherapy and radiotherapy.

Boosting Activity and Selectivity of CO2 Electroreduction by Pre-Hydridizing Pd Nanocubes.

The electrochemical CO2 reduction reaction (CO2 RR) to syngas represents a promising solution to mitigate CO2 emissions and manufacture value-added chemicals. Palladium (Pd) has been identified as a potential candidate for syngas production via CO2 RR due to its transformation to Pd hydride under CO2 RR conditions, however, the pre-hydridized effect on the catalytic properties of Pd-based electrocatalysts has not been investigated. Herein, pre-hydridized Pd nanocubes (PdH0.40 ) supported on carbon black (PdH0.40 NCs/C) are directly prepared from a chemical reduction method. Compared with Pd nanocubes (Pd NCs/C), PdH0.40 NCs/C presented an enhanced CO2 RR performance due to its less cathodic phase transformation revealed by the in situ X-ray absorption spectroscopy. Density functional theory calculations revealed different binding energies of key reaction intermediates on PdH0.40 NCs/C and Pd NCs/C. Study of the size effect further suggests that NCs of smaller sizes show higher activity due to their more abundant active sites (edge and corner sites) for CO2 RR. The pre-hydridization and reduced NC size together lead to significantly improved activity and selectivity of CO2 RR.

New insights into two yeast BDHs from the PDH subfamily as aldehyde reductases in context of detoxification of lignocellulosic aldehyde inhibitors.

At least 24 aldehyde reductases from Saccharomyces cerevisiae have been characterized and most function in in situ detoxification of lignocellulosic aldehyde inhibitors, but none is classified into the polyol dehydrogenase (PDH) subfamily of the medium-chain dehydrogenase/reductase (MDR) superfamily. This study confirmed that two (2R,3R)-2,3-butanediol dehydrogenases (BDHs) from industrial (denoted Y)/laboratory (denoted B) strains of S. cerevisiae, Bdh1p(Y)/Bdh1p(B) and Bdh2p(Y)/Bdh2p(B), were members of the PDH subfamily with an NAD(P)H binding domain and a catalytic zinc binding domain, and exhibited reductive activities towards lignocellulosic aldehyde inhibitors, such as acetaldehyde, glycolaldehyde, and furfural. Especially, the highest enzyme activity towards acetaldehyde by Bdh2p(Y) was 117.95 U/mg with cofactor nicotinamide adenine dinucleotide reduced (NADH). Based on the comparative kinetic property analysis, Bdh2p(Y)/Bdh2p(B) possessed higher specific activity, substrate affinity, and catalytic efficiency towards glycolaldehyde than Bdh1p(Y)/Bdh1p(B). This was speculated to be related to their 49% sequence differences and five nonsynonymous substitutions (Ser41Thr, Glu173Gln, Ile270Leu, Ile316Met, and Gly317Cys) occurred in their conserved NAD(P)H binding domains. Compared with BDHs from a laboratory strain, Bdh1p(Y) and Bdh2p(Y) from an industrial strain displayed five nonsynonymous mutations (Thr12, Asn61, Glu168, Val222, and Ala235) and three nonsynonymous mutations (Ala34, Ile96, and Ala369), respectively. From a first analysis with selected aldehydes, their reductase activities were different from BDHs of laboratory strain, and their catalytic efficiency was higher towards glycolaldehyde and lower towards acetaldehyde. Comparative investigation of kinetic properties of BDHs from S. cerevisiae as aldehyde reductases provides a guideline for their practical applications in in situ detoxification of aldehyde inhibitors during lignocellulose bioconversion.Key Points• Two yeast BDHs have enzyme activities for reduction of aldehydes.• Overexpression of BDHs slightly improves yeast tolerance to acetaldehyde and glycolaldehyde.• Bdh1p and Bdh2p differ in enzyme kinetic properties.• BDHs from strains with different genetic backgrounds differ in enzyme kinetic properties.