Malate Dehydrogenase Research Articles

Aerobic and anaerobic poise of white swimming muscles of the deep-diving scalloped hammerhead shark: comparison to sympatric coastal and deep-water species

Scalloped hammerhead sharks (Sphyrna lewini) routinely perform rapid dives to forage on mesopelagic prey. These deep dives consist of intensive swimming followed by recovery periods in the surface mixed layer. Swimming muscle temperature profiles suggest that S. lewini suppresses gill function as a means to reduce convective heat loss during dives into cool water. Such intensive swimming behavior coupled with reduced respiration prompted us to test whether the aerobic and anaerobic metabolic capacities of the white swimming muscle tissue of this species are greater than those of other shark species from the same region. The activities of key enzymes used in aerobic and anaerobic metabolism provide an indirect indicator of the metabolic potential (“poise”) of a tissue. Here we measured the maximal activities [international units (µmol substrate converted to product per min, U) per gram of wet tissue mass at 10°C] of the citric acid cycle enzymes citrate synthase (CS) and malate dehydrogenase (MDH) and glycolytic enzymes pyruvate kinase (PK) and lactate dehydrogenase (LDH) from white swimming muscle of S. lewini. Enzyme activities, and ratios of these enzyme activities that indicate relative indexes of aerobic to anaerobic capacity, were compared to those measured in three sympatric coastal carcharhinid sharks and two deep-dwelling species, Echinorhinus cookei and Hexanchus griseus. This is the first report of swimming-muscle enzyme activity for these deep-dwelling species. In comparison to the other species, S. lewini had significantly higher activities of both LDH and MDH in the white muscle, and a higher MDH/CS ratio. The high LDH activities suggest that the white muscle of S. lewini relies on relatively high rates of anaerobic ATP production, with would result in build up of high lactate levels, during deep foraging dives. High MDH activity in S. lewini white muscle suggests the potential for lactate levels to be rapidly reduced when aerobic conditions are restored while in the surface mixed layer between dives. These biochemical characteristics may enable S. lewini to swim rapidly while suppressing gill function during deep dives and thereby exploit a very different ecological niche from sympatric shark species (e.g., coastal carcharhinids) and hunt more rapidly via faster swimming for deep-water prey compared to species that permanently inhabit deep depths.

Effect of dietary Anabaena supplementation on nutrient utilization, metabolism and oxidative stress response in Catla catla fingerlings

A 60-day feeding trial was conducted to evaluate the effects of dietary Anabaena blue-green algae (ABGA) meal on the growth performance, digestibility, and physio-metabolic responses of Catla catla fingerlings (initial average weight 9.45 ± 0.15 g). Six iso-nitrogenous (30% crude protein) and iso-caloric (378.09 Kcal. digestible energy/100 g) diets were formulated: a control diet (A0, 0% ABGA) and five experimental diets with varying ABGA inclusion levels (A3: 3%, A6: 6%, A9: 9%, A12: 12%, A15: 15%). The results demonstrated that there were no significant differences (P > 0.05) in percentage weight gain (PWG), specific growth rate (SGR), protein efficiency ratio (PER), and feed conversion ratio (FCR) among the experimental groups. Additionally, dietary ABGA did not significantly affect (P > 0.05) body carcass composition among different groups. However, amylase activity significantly decreased (P < 0.05) in the A12 and A15 fed groups, whereas lipase and protease activities remained insignificant (P > 0.05) across all groups. Notably, oxidative stress responses (SOD; superoxide dismutase and CAT; catalase), carbohydrate metabolic enzymes (LDH; lactate dehydrogenase and MDH; malate dehydrogenase), and serum glucose levels increased significantly (P < 0.05) with higher ABGA inclusion. Conversely, serum albumin content significantly decreased (P < 0.05) in the ABGA-fed groups. There were no significant differences (P > 0.05) observed in serum total protein, albumin/globulin (A/G) ratio, aspartate aminotransferase (AST), and alanine aminotransferase (ALT) activities among the experimental groups. Hematological parameters revealed that RBC (red blood cell) count, hemoglobin (Hb) concentration, and packed cell volume (PCV) significantly decreased (P < 0.05), while WBC (white blood cell) count significantly (P < 0.05) increased with higher dietary ABGA inclusion. In conclusion, the inclusion of dietary ABGA up to 15% did not impair nutrient utilization and supported normal growth performance in C. catla fingerlings. However, higher inclusion levels may have a detrimental effect on their growth, nutrient utilization, and physio-metabolic responses.

Evaluation and Validation of Reliable Reference Genes for Quantitative Real-Time PCR Analysis of the Gene Expression in Macadamia integrifolia

Macadamia is an economically significant crop, with its kernel oil being abundant in monounsaturated fatty acids (MUFA). Analyzing the expression of genes related to MUFA biosynthesis is essential for understanding the complex regulatory networks in Macadamia. However, there are few reports on the identification of suitable reference genes for use as internal controls in this species. Consequently, selecting a reliable reference gene for gene expression studies under various conditions is critical. In this study, we evaluated the expression stability of 11 traditional housekeeping genes: α-tubulin (TUBa), β-tubulin (TUBb), malate dehydrogenase (MDH), 18S ribosomal RNA (18S), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), α-elongation factor 1 (EF1a), β-elongation factor 1 (EF1b), ubiquitin (UBQ), ubiquitin-conjugating enzyme (UBC), cyclophilin (CYP), and actin (ACT) under abiotic stresses, hormonal treatments and in variety of plant tissues using the online tool RefFinder, which integrates four commonly used software programs: ΔCt, geNorm (version 3.4), NormFinder (version 0953), and BestKeeper (version 1.0). A comprehensive expression stability ranking was established by integrating results from these four methods based on the geometric mean. The findings indicated that ACT was the most stable gene across all samples, including those subjected to cold stress, NaCl stress, PEG stress, ABA treatment, MeJA treatment, and both stem and leaf tissues. EF1b was identified as the most stable gene in GA treatment and heat stress samples, while UBC and CYP were ranked highest in ethrel treatment and root tissue samples, respectively. Finally, the reliability of these findings was further validated using the target gene SAD through qRT-PCR. In summary, this study evaluated and validated appropriate reference genes for qRT-PCR, which will facilitate future investigations into the molecular mechanisms in Macadamia.

The characterization of ancient Methanococcales malate dehydrogenases reveals that strong thermal stability prevents unfolding under intense γ-irradiation.

Malate dehydrogenases (MalDH) (EC.1.1.1.37), which are involved in the conversion of oxaloacetate to pyruvate in the tricarboxylic acid cycle, are a relevant model for the study of enzyme evolution and adaptation. Likewise, a recent study showed that Methanococcales, a major lineage of Archaea, is a good model to study the molecular processes of proteome thermoadaptation in prokaryotes. Here, we use ancestral sequence reconstruction and paleoenzymology to characterize both ancient and extant MalDHs. We observe a good correlation between inferred optimal growth temperatures (OGTs) and experimental optimal temperatures for activity (A-Topt). In particular, we show that the MalDH present in the ancestor of Methanococcales was hyperthermostable and had an A-Topt of 80°C, consistent with a hyperthermophilic lifestyle. This ancestor gave rise to two lineages with different thermal constraints, one remaining hyperthermophilic while the other underwent several independent adaptations to colder environments. Surprisingly, the enzymes of the first lineage have retained a thermoresistant behavior (i.e., strong thermostability and high A-Topt), whereas the ancestor of the second lineage shows a strong thermostability, but a reduced A-Topt. Using mutants, we mimic the adaptation trajectory towards mesophily and show that it is possible to significantly reduce the A-Topt without altering the thermostability of the enzyme by introducing a few mutations. Finally, we reveal an unexpected link between thermostability and the ability to resist γ-irradiation-induced unfolding.

Exploring the ameliorative potential of rutin against High-Sucrose Diet-induced oxidative stress and reproductive toxicity in Drosophila melanogaster

Sucrose is a vital ingredient in numerous food items consumed regularly. However, exposure to excessive sucrose for a prolonged period can promote health issues. The reproductive system has a delicate physiology that can be targeted by various chemical stressors, including sucrose. Hence, the present in vivo study aims to unveil the impacts of the High-Sucrose Diet (HSD) on the reproductive fitness of Drosophila melanogaster. In addition, the present work has also assessed the protective potential of a bioactive compound, rutin, against it. Here, 1st instar larvae were exposed to HSD (30%) alone and in combination with rutin (100-300µM) till their adult stage. HSD disturbed sex comb morphology in adult males, while fecundity and hatchability of eggs in females. Moreover, HSD triggered gonadal ROS production, oxidative stress, and modulated endogenous antioxidants such as SOD, catalase, and glutathione in both sexes. Nuclear fragmentation and tissue injuries, along with protein and lipid oxidation, were also apparent. Elevated levels of cytosolic Iron suggested an active Fenton reaction in adults. Further, HSD modulated the activities of reproductive and metabolic mediators, including vitellogenin, malate dehydrogenase, glucose-6-phosphate dehydrogenase, and angiotensin-converting enzymes that are critical to overall reproductive fitness. Interestingly, co-treatment with rutin, mainly at 200µM, mitigated these adverse effects and restored reproductive fitness. The protective potential of rutin might be attributed to its ability to normalize redox homeostasis, reduce oxidative stress, and optimize critical enzymes involved in reproductive physiology. These findings suggest that rutin has potential therapeutic implications to counteract the reproductive hazards induced by HSD.

Insights into the antifungal activity and mechanisms of cinnamon components against Aspergillus flavus and Penicillium citrinum

Fungal spoilage of food and the excessive use of chemical disinfectants serves potential adverse effects on human health and the environment. Consequently, there is a growing interest in exploring natural alternatives, particularly plant-derived antimicrobial preservatives. Cinnamon extracts are known for their antifungal activity, but most research has focused on essential oils, rarely on other bioactive components. This study assessed the antifungal activity and underlying mechanisms of four components—trans-cinnamaldehyde, cis-2-methoxycinnamic acid, coumarin, and o-methoxycinnamaldehyde—extracted from Cinnamomum cassia Presl (cinnamon) against Aspergillus flavus and Penicillium citrinum. These cinnamon components can inhibit the two fungi strains at the minimum inhibitory concentration ranged from 0.30 to 8.55 mmol/L. These components can disrupt fungal cell membranes by enhancing relative electrical conductivity and cytoplasmic content leakage, reducing ergosterol content, and increasing malondialdehyde level. Additionally, they can affect fungal cell wall integrity, leading to the leakage of alkaline phosphatase and alterations in the contents of β-1,3-glucan and chitin. Moreover, the cinnamon components influenced the activities of malate dehydrogenase, succinate dehydrogenase, as well as adenosine triphosphate levels. The observed suppression of fungal contamination in A. flavus and P. citrinum suggests that these cinnamon components as potential natural antifungal agents.

The Key Enzymes of Carbon Metabolism and the Glutathione Antioxidant System Protect Yarrowia lipolytica Yeast Against pH-Induced Stress

In this study, we first thoroughly assayed the response of the key enzymes of energy metabolism and the antioxidant system in Yarrowia lipolytica yeast at extreme pH. The activity of the tricarboxylic acid cycle enzymes, namely NAD-dependent isocitrate dehydrogenase, aconitate hydratase, NAD-dependent malate dehydrogenase, and fumarate hydratase, NADPH-producing enzymes of glucose-6-P dehydrogenase and NADP-dependent isocitrate dehydrogenase, and the enzymes of the glutathione system was assessed. All the enzymes that were tested showed a significant induction contrary to some decrease in the aconitate hydratase activity with acidic and alkaline stress. It is probable that a change in the enzyme activity in the mitochondria matrix is involved in the regulation of the cellular metabolism of Y. lipolytica, which allows the species to prosper at an extreme ambient pH. It distinguishes it from any other type of ascomycete. A close relationship between the induction of the Krebs cycle enzymes and the key enzymes of the glutathione system accompanied by an increased level of reduced glutathione was shown. The assumption that the increased activity of the Krebs cycle dehydrogenases and promotion of the pentose phosphate pathway at pH stress launches a set of events determining the adaptive response of Y. lipolytica yeast.

MDH2 Promotes Hepatocellular Carcinoma Growth Through Ferroptosis Evasion via Stabilizing GPX4.

The crosstalk between tumor progression and ferroptosis is largely unknown. Here, we identify malate dehydrogenase 2 (MDH2) as a key regulator of ferroptosis. MDH2 deficiency inhibits the growth of hepatocellular carcinoma (HCC) cells and enhances their sensitivity to ferroptosis induced by RAS-selective lethal 3 (RSL3), a compound known to cause ferroptosis. MDH2 knock-down enhances RSL3-induced intracellular reactive oxygen species, free iron ions and lipid per-oxides levels, leading to HCC ferroptotic cell death which is rescued by ferrostatin-1 and iron chelator deferiprone. Importantly, the inhibition of HCC cell growth caused by MDH2 deficiency is partially rescued by ferroptosis blockade. Mechanistically, MDH2 resists RSL3-induced ferroptosis sensitivity dependent on glutathione peroxidase 4 (GPX4), an enzyme responsible for scavenging lipid peroxides, which is stabilized by MDH2 in HCC. The protein expressions of MDH2 and GPX4 are positively correlated with each other in HCC cell lines. Furthermore, through our UALCAN website analysis, we found that MDH2 and GPX4 are highly expressed in HCC samples. These findings reveal a critical mechanism by which HCC evades ferroptosis via MDH2-mediated stabilization of GPX4 to promote tumor progression and underscore the potential of MDH2 inhibition in combi-nation with ferroptosis inducers for the treatment of HCC.

Dexmedetomidine Ameliorates Myocardial Ischemia-Reperfusion Injury by Inhibiting MDH2 Lactylation via Regulating Metabolic Reprogramming.

Myocardial ischemia-reperfusion injury (MIRI) significantly worsens the outcomes of patients with cardiovascular diseases. Dexmedetomidine (Dex) is recognized for its cardioprotective properties, but the related mechanisms, especially regarding metabolic reprogramming, have not been fully clarified. A total of 60 patients with heart valve disease are randomly assigned to Dex or control group. Blood samples are collected to analyze cardiac injury biomarkers and metabolomics. In vivo and vitro rat models of MIRI are utilized to assess the effects of Dex on cardiac function, lactate production, and mitochondrial function. It is found that postoperative CK-MB and cTNT levels are significantly lower in the Dex group. Metabolomics reveals that Dex regulates metabolic reprogramming and reduces lactate level. In Dex-treated rats, the myocardial infarction area is reduced, and myocardial contractility is improved. Dex inhibits glycolysis, reduces lactate, and improves mitochondrial function following MIRI. Lactylation proteomics identifies that Dex reduces the lactylation of Malate Dehydrogenase 2（MDH2), thus alleviating myocardial injury. Further studies reveal that MDH2 lactylation induces ferroptosis, leading to MIRI by impairing mitochondrial function. Mechanistic analyses reveal that Dex upregulates Nuclear Receptor Subfamily 3 Group C Member 1（NR3C1)phosphorylation, downregulates Pyruvate Dehydrogenase Kinase 4 (PDK4), and reduces lactate production and MDH2 lactylation. These findings provide new therapeutic targets and mechanisms for the treatment for MIRI.

Expression of pyruvate kinase, malate and octopine dehydrogenase genes in the gills of the Mediterranean mussel Mytilus galloprovincialis (Lamarck, 1819) under conditions of hypoxia and reoxygenation

The effect of hypoxia on the expression level of pyruvate kinase (PKM), octopine dehydrogenase (OcDH) and malate dehydrogenase (MDH) genes in the gill tissue of the Mediterranean mussel Mytilus galloprovincialis (L., 1819) was studied experimentally. The control group of mollusks was kept at 9–10°C and the oxygen level in the water was 8.5 mgO2 l–1. Experimental – at 9–10°C and 2.2 mgO2 l–1. The exposure was 24 and 72 hours. Some of the individuals were subsequently subjected to the reoxygenation procedure. Under conditions of hypoxia, the expression level of OcDH and MDH genes increased by 3 and 2 times, respectively (p 0.05). At the same time, OcDH expression showed sensitivity to the oxygen content in the medium. Under the conditions of reoxygenation, the process was completely suppressed. The expression of the PKM gene, on the contrary, did not depend on hypoxic effects and remained at the level of control values.

Metabolic regulation of the glioblastoma stem cell epitranscriptome by malate dehydrogenase 2

Tumors reprogram their metabolism to generate complex neoplastic ecosystems. Here, we demonstrate that glioblastoma (GBM) stem cells (GSCs) display elevated activity of the malate-aspartate shuttle (MAS) and expression of malate dehydrogenase 2 (MDH2). Genetic and pharmacologic targeting of MDH2 attenuated GSC proliferation, self-renewal, and invivo tumor growth, partially rescued by aspartate. Targeting MDH2 induced accumulation of alpha-ketoglutarate (αKG), a critical co-factor for dioxygenases, including the N6-methyladenosine (m6A) RNA demethylase AlkB homolog 5, RNA demethylase (ALKBH5). Forced expression of MDH2 increased m6A levels and inhibited ALKBH5 activity, both rescued by αKG supplementation. Reciprocally, targeting MDH2 reduced global m6A levels with platelet-derived growth factor receptor-β (PDGFRβ) as a regulated transcript. Pharmacological inhibition of MDH2 in GSCs augmented efficacy of dasatinib, an orally bioavailable multi-kinase inhibitor, including PDGFRβ. Collectively, stem-like tumor cells reprogram their metabolism to induce changes in their epitranscriptomes and reveal possible therapeutic paradigms.

Engineering Yarrowia lipolytica to Produce l-Malic Acid from Glycerol.

The declining availability of cheap fossil-based resources has sparked growing interest in the sustainable biosynthesis of organic acids. l-Malic acid, a crucial four-carbon dicarboxylic acid, finds extensive applications in the food, chemical, and pharmaceutical industries. Synthetic biology and metabolic engineering have enabled the efficient microbial production of l-malic acid, albeit not in Yarrowia lipolytica, an important industrial microorganism. The present study aimed to explore the potential of this fungal species for the production of l-malic acid. First, endogenous biosynthetic genes and heterologous transporter genes were overexpressed in Y. lipolytica to identify bottlenecks in the l-malic acid biosynthesis pathway grown on glycerol. Second, overexpression of isocitrate lyase, malate synthase, and malate dehydrogenase in the glyoxylate cycle pathway and introduction of a malate transporter from Schizosaccharomyces pombe significantly boosted l-malic acid production, which reached 27.0 g/L. A subsequent increase to 37.0 g/L was attained through shake flask medium optimization. Third, adaptive laboratory evolution allowed the engineered strain Po1g-CEE2+Sp to tolerate a lower pH and to accumulate a higher amount of l-malic acid (56.0 g/L). Finally, when scaling up to a 5 L bioreactor, a titer of 112.5 g/L was attained. In conclusion, this study demonstrates for the first time the successful production of l-malic acid in Y. lipolytica by combining metabolic engineering and laboratory evolution, paving the way for large-scale sustainable biosynthesis of this and other organic acids.

ME2 Deficiency Is Associated With Recessive Neurodevelopmental Disorder.

Malate is an important dicarboxylic acid produced from fumarate in the tricarboxylic acid cycle. Deficiencies of fumarate hydrolase (FH) and malate dehydrogenase (MDH), responsible for malate formation and metabolism, respectively, are known to cause recessive forms of neurodevelopmental disorders (NDDs). The malic enzyme isoforms, malic enzyme 1 (ME1) and 2 (ME2), are required for the conversion of malate to pyruvate. To date, there have been no reports linking deficiency of either malic enzyme isoforms to any Mendelian disease in humans. We report a patient presenting with NDD, subtle dysmorphic features, resolved dilated cardiomyopathy, and mild blood lactate elevation. Whole exome sequencing (WES) revealed a homozygous frameshift variant (c.1379_1380delTT, p.Phe460fs*22) in the malic enzyme 2 (ME2) gene resulting in truncated and unstable ME2 protein in vitro. Subsequent deletion of the yeast ortholog of human ME2 (hME2) resulted in growth arrest, which was rescued by overexpression of hME2, strongly supporting an important role of ME2 in mitochondrial function. Our results also support the pathogenicity and candidacy of the ME2 gene and variant in association with NDD. To our knowledge, this is the first report of a Mendelian human disease resulting from a biallelic variant in the ME encoding gene. Future studies are warranted to confirm ME2-associated recessive NDD.

Visnagin alleviates rheumatoid arthritis via its potential inhibitory impact on malate dehydrogenase enzyme: in silico, in vitro, and in vivo studies

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disorder. The present study aimed to evaluate the in silico, in vitro, and in vivo inhibitory effect of visnagin on malate dehydrogenase activity and elucidate its inflammatory efficacy when combined with methotrexate in the RA rat model. The molecular docking, ADMET simulations, MDH activity, expression, and X-ray imaging were detected. Moreover, CRP, RF, (anti-CCP) antibody, (TNF-α), (IL-6), (IL-17), and (IL-10) were evaluated. The expression levels of MMP3 and FOXP3 genes and CD4, CD25, and CD127 protein levels were assessed. Histological assessment of ankle joints was evaluated. The results revealed that visnagin showed reversible competitive inhibition on MDH with inhibitory constant (Ki) equal to 141 mM with theoretical IC50 equal to 1202.7 mM, LD50 equal to 155.39 mg/kg, and LD25 equal to 77.69 mg/kg. In vivo studies indicated that visnagin exhibited anti-inflammatory effects through decreasing MDH1 activity and expression and induced proliferation of anti-inflammatory CD4+CD25+FOXP3 regulatory T cells with increasing the anti-inflammatory cytokine IL-10 levels. Moreover, visnagin reduced the levels of inflammatory cytokines and the immuno-markers. Our findings elucidate that visnagin exhibits an anti-inflammatory impact against RA through its ability to inhibit the MDH1 enzyme, improve methotrexate efficacy, and reduce oxidative stress.Graphical

Effects of four-week lasting aerobic treadmill training on hepatic injury biomarkers, oxidative stress parameters, metabolic enzymes activities and histological characteristics in liver tissue of hyperhomocysteinemic rats.

Disruptions in homocysteine (Hcy) metabolism may increase the liver's susceptibility to developing conditions such as alcoholic liver disease, viral hepatitis, hepatocellular carcinoma (HCC), and cirrhosis. The aim of this study was to examine effects of aerobic treadmill training on hepatic injury biomarkers in sera, oxidative stress parameters, the activity of metabolic enzymes, and histological characteristics in the liver tissue of rats with experimentally induced hyperhomocysteinemia. Male Wistar albino rats were divided into four groups (N = 10, per group): C-saline 0.2mL/day sc. 2×/day for 14days + saline 0.5mL ip.1×/day for 28days; H-homocysteine 0.45µmol/g b.w. 2×/day for 14days + saline 0.5mL ip.1×/day for 28days; CPA-saline 0.2mL/day sc. 2×/day for 14days + aerobic treadmill training for 28days; and HPA-homocysteine 0.45µmol/gb.w. 2×/day for 14days + aerobic treadmill training for 28days. The serum albumin concentration was decreased in both physically active (PA) groups compared to sedentary groups. Concentration of malondialdehyde in liver tissue homogenates was lower in both PA groups compared to the H group. The total lactate dehydrogenase and malate dehydrogenase activities were significantly elevated in the HPA group compared to the C and H groups. Activities of aminotransferases in sera samples, and activities of catalase and superoxide dismutase in liver tissue did not significantly differ between groups. No significant histological changes were found in liver tissue in groups. This study demonstrated that aerobic treadmill training can reduce lipid peroxidation in liver tissue under hyperhomocysteinemic conditions, providing a protective effect. However, hyperhomocysteinemia can alter energy metabolism during aerobic exercise, shifting it toward anaerobic pathways and leading to elevated lactate dehydrogenase activity in the liver. Given that conditions like hyperhomocysteinemia are associated with an increased risk of cardiovascular diseases and liver damage, understanding how exercise influences these dynamics could guide therapeutic approaches.

Antibacterial mechanism of atmospheric cold plasma against Pseudomonas fluorescens and Pseudomonas putida and its preservation application on in-packaged red shrimp paste

This study aimed to investigate the antibacterial mechanism of atmospheric cold plasma (ACP) against Pseudomonas fluorescens and Pseudomonas putida and its preservation effect on red shrimp paste. A reactive species (RS) assay showed that O3, H2O2, and total nitric oxide were generated after ACP treatment, which possessed great potential for antibacterial and food preservation. In vitro antibacterial results showed that excess RS inhibited bacterial activity through cell membrane damage. Molecular docking predictions and enzyme activity assays indicated that ACP-induced RS might deactivate dehydrogenases (such as malic dehydrogenase) by oxidatively modifying the active sites. Fluorescence quantification experiments validated the damage of RS to dsDNA. Further preservation tests on shrimp paste demonstrated that ACP treatment significantly delayed the increase in total viable count, Pseudomonas count, and total volatile basic‑nitrogen during refrigeration. This study deepened the understanding of the antibacterial mechanism of ACP and highlighted its potential application as a new preservation method.

Engineering the by-products pathway in Aureobasidium pullulans for highly purified polymalic acid fermentation with concurrent recovery of l-malic acid

The fermentation of polymalic acid (PMA) by Aureobasidium pullulans, followed by acid hydrolysis to release the monomer l-malic acid (l-MA), has emerged as a promising process for the bio-based production of l-MA. However, the presence of specific by-products significantly affects the quality of the final products. In this study, chassis strains harboring an overexpressed endogenous malate dehydrogenase gene (ApMDH2) were engineered to delete key genes involved in the pullulan, melanin, and liamocin biosynthetic pathways. Furthermore, to enhance PMA synthesis productivity and prevent intracellular NADPH accumulation, an irreversible trans-hydrogenase transformation system was designed to efficiently convert NADPH to NADH. In fed-batch fermentation, the engineered strain produced the highest PMA titer (194.3 ± 1.1 g/L) and l-MA yield (0.89 ± 0.01 g/g) with an increased productivity (1.45 ± 0.06 g/L∙h). Moreover, a total of 86.19 % l-MA, with a purity of 99.7 %, was successfully extracted from fermentation broth.

Characteristics of Myocardial Structure and Central Carbon Metabolism during the Early and Compensatory Stages of Cardiac Hypertrophy.

Cardiac hypertrophy is a classical forerunner of heart failure and myocardial structural and metabolic remodeling are closely associated with cardiac hypertrophy. We aim to investigate the characteristics of myocardial structure and central carbon metabolism of cardiac hypertrophy at different stages. Using echocardiography and pathological staining, early and compensatory cardiac hypertrophy were respectively defined as within 7 days and from 7 to 14 days after transverse aortic constriction (TAC) in mice. Among mass-spectrometry-based metabolomics, we identified 45 central carbon metabolites. Differential metabolite analysis showed that six metabolites, including citrate, cis-aconitate and so on, decreased significantly on day 1 after TAC. Ten metabolites, including l-lactate, (S)-2-hydroxyglutarate and so on, were obviously changed on days 10 and 14. Pathway analysis showed that these metabolites were involved in seven metabolic pathways, including carbohydrates, amino acids and so on. Western blot showed the expression of ATP-citrate lyase, malate dehydrogenase 1 and lactate dehydrogenase A in myocardium changed markedly on day 3, while the phosphorylation level of AMP-activated protein kinase did not show significantly difference. We hope our research will promote deeper understanding and early diagnosis of cardiac hypertrophy in clinical practice. All raw data were deposited in MetaboLights (MTBLS10555).

Malate dehydrogenase as a multi-purpose target for drug discovery.

Malate dehydrogenase (MDH) enzymes play critical roles in cellular metabolism, facilitating the reversible conversion of malate to oxaloacetate using NAD+/NADH as a cofactor. The two human isoforms of MDH have roles in the citric acid cycle and the malate-aspartate shuttle, and thus both are key enzymes in aerobic respiration as well as regenerating the pool of NAD+ used in glycolysis. This review highlights the potential of MDH as a therapeutic drug target in various diseases, including metabolic and neurological disorders, cancer, and infectious diseases. The most promising molecules for targeting MDH have been examined in the context of human malignancies, where MDH is frequently overexpressed. Recent studies have led to the identification of several antagonists, some of which are broad MDH inhibitors while others have selectivity for either of the two human MDH isoforms. Other promising compounds have been studied in the context of parasitic MDH, as inhibiting the function of the enzyme could selectively kill the parasite. Research is ongoing with these chemical scaffolds to develop more effective small-molecule drug leads that would have great potential for clinical applications.

Malate dehydrogenase: a story of diverse evolutionary radiation.

Malate dehydrogenase (MDH) is a ubiquitous enzyme involved in cellular respiration across all domains of life. MDH's ubiquity allows it to act as an excellent model for considering the history of life and how the rise of aerobic respiration and eukaryogenesis influenced this evolutionary process. Here, we present the diversity of the MDH family of enzymes across bacteria, archaea, and eukarya, the relationship between MDH and lactate dehydrogenase (LDH) in the formation of a protein superfamily, and the connections between MDH and endosymbiosis in the formation of mitochondria and chloroplasts. The development of novel and powerful DNA sequencing techniques has challenged some of the conventional wisdom underlying MDH evolution and suggests a history dominated by gene duplication, horizontal gene transfer, and cryptic endosymbiosis events and adaptation to a diverse range of environments across all domains of life over evolutionary time. The data also suggest a superfamily of proteins that do not share high levels of sequential similarity but yet retain strong conservation of core function via key amino acid residues and secondary structural components. As DNA sequencing and 'big data' analysis techniques continue to improve in the life sciences, it is likely that the story of MDH will continue to refine as more examples of superfamily diversity are recovered from nature and analyzed.