Topic
Pyruvate kinase
About: Pyruvate kinase is a research topic. Over the lifetime, 5683 publications have been published within this topic receiving 180020 citations. The topic is also known as: ATP:pyruvate 2-O-phosphotransferase & phosphoenolpyruvate kinase.
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55 citations
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TL;DR: Glycogenolysis versus gluconeogenesis correlates with metabolism of hyperpolarized dihydroxyacetone, and a ratio of glycolytic to gluconeogenic products distinguished the gluc oneogenic from glycogenolytic state in these functioning livers.
55 citations
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TL;DR: Changes induced in intracellular concentrations of glycolytic intermediates by alterations in pH revealed that the decrease in the rate of gly colysis in these organisms at acidic pH values was caused by the inhibition, or damage, of the ATP-glucose phosphotransferase activity.
55 citations
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TL;DR: The finding that some energy may be obtained via increased aminoacid catabolism, leading to the generation of tricarboxylic acid (TCA) cycle intermediates in aphylogenetically ancient, air-breathing fish is indicated.
Abstract: The potential importance of carbohydrates and amino acids as fuels during periods of fasting and aestivation in the African lungfish, Protopterus dolloi, were examined. No significant decreases in tissue glycogen levels were observed following 60 days of fasting or aestivation, suggesting lungfish may undergo 'glycogen sparing'. Yet glycogenolysis may be important during aestivation based on the differing responses of two flux-generating enzymes of the glycolytic pathway, hexokinase (HK) and pyruvate kinase (PK). PK is required for glycogen breakdown whereas HK is not. HK activity is significantly down-regulated in the heart and gill tissues during aestivation, while PK activity is sustained. The significant negative correlation between the activity of HK and glucose levels in the heart of aestivating lungfish suggests HK may be regulated by glucose concentrations. There was no indication of anaerobic glycolytic flux during aestivation as lactate did not accumulate in any of the tissues examined, and no significant induction of lactate dehydrogenase (LDH)activity was observed. The increase in glutamate dehydrogenase (GDH) and aspartate aminotransferase (Asp-AT) activities in the liver of aestivating P. dolloi suggests some energy may be obtained via increased aminoacid catabolism, leading to the generation of tricarboxylic acid (TCA) cycle intermediates. These findings indicate the importance of both carbohydrate and amino acid fuel stores during aestivation in aphylogenetically ancient, air-breathing fish.
54 citations
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22 Feb 2017TL;DR: This work identifies key transcriptomic and proteomic features of the pneumococcal endogenous oxidative stress response and proposes that LctO/SpxB-generated H2O2 functions as a signaling molecule to downregulate capsule production and drive altered flux through sugar utilization pathways.
Abstract: The catalase-negative, facultative anaerobe Streptococcus pneumoniae D39 is naturally resistant to hydrogen peroxide (H2O2) produced endogenously by pyruvate oxidase (SpxB). Here, we investigate the adaptive response to endogenously produced H2O2. We show that lactate oxidase, which converts lactate to pyruvate, positively impacts pyruvate flux through SpxB and that ΔlctO mutants produce significantly lower H2O2. In addition, both the SpxB pathway and a candidate pyruvate dehydrogenase complex (PDHC) pathway contribute to acetyl coenzyme A (acetyl-CoA) production during aerobic growth, and the pyruvate format lyase (PFL) pathway is the major acetyl-CoA pathway during anaerobic growth. Microarray analysis of the D39 strain cultured under aerobic versus strict anaerobic conditions shows upregulation of spxB, a gene encoding a rhodanese-like protein (locus tag spd0091), tpxD, sodA, piuB, piuD, and an Fe-S protein biogenesis operon under H2O2-producing conditions. Proteome profiling of H2O2-induced sulfenylation reveals that sulfenylation levels correlate with cellular H2O2 production, with endogenous sulfenylation of ≈50 proteins. Deletion of tpxD increases cellular sulfenylation 5-fold and has an inhibitory effect on ATP generation. Two major targets of protein sulfenylation are glyceraldehyde-3-phosphate dehydrogenase (GapA) and SpxB itself, but targets also include pyruvate kinase, LctO, AdhE, and acetate kinase (AckA). Sulfenylation of GapA is inhibitory, while the effect on SpxB activity is negligible. Strikingly, four enzymes of capsular polysaccharide biosynthesis are sulfenylated, as are enzymes associated with nucleotide biosynthesis via ribulose-5-phosphate. We propose that LctO/SpxB-generated H2O2 functions as a signaling molecule to downregulate capsule production and drive altered flux through sugar utilization pathways. IMPORTANCE Adaptation to endogenous oxidative stress is an integral aspect of Streptococcus pneumoniae colonization and virulence. In this work, we identify key transcriptomic and proteomic features of the pneumococcal endogenous oxidative stress response. The thiol peroxidase TpxD plays a critical role in adaptation to endogenous H2O2 and serves to limit protein sulfenylation of glycolytic, capsule, and nucleotide biosynthesis enzymes in S. pneumoniae.
54 citations