Pyruvate reductases dehydrogenase

The lactate produced mainly in muscle diffuses in blood and reaches the heart where the principal function of LDH-H is oxidizing lactate to pyruvate, which can then be utilized through the Krebs cycle. In fact, if blood concentrations of lactate are increased, the uptake of that metabolite by the heart is also increased. Thus, the H-type is the true lactic dehydrogenase, while the M-type is really a pyruvic reductase. 

Mutation of the dihydrolipoate reductase component impairs decarboxylation of branched-chain a-keto acids, of pyruvate, and of a-ketoglutarate. In intermittent branched-chain ketonuria, the a-keto acid decarboxylase retains some activity, and symptoms occur later in life. The impaired enzyme in isovaleric acidemia is isovaleryl-CoA dehydrogenase (reaction 3, Figure 30-19). Vomiting, acidosis, and coma follow ingestion of excess protein. Accumulated... 

Fig. 14.1. Role ofthe pyruvate dehydrogenase complex (PDC) during aerobic/ anaerobic transitions in the development of Ascaris suum. PDC, pyruvate dehydrogenase complex AD, acyl CoA dehydrogenase ER, enoyl CoA reductase FR, fumarate reductase SDH, succinate dehydrogenase.

Fig. 1. Modification of plant metabolic pathways for the synthesis of poly(3HB) and poly(3HB-co-3HV). The pathways created or enhanced by the expression of transgenes are highlighted in bold, while endogenous plant pathways are in plain letters. The various transgenes expressed in plants are indicated in italics. The ilvA gene encodes a threonine deaminase from E. coli. The phaARe, phaBRe, and phaCRe genes encode a 3-ketothiolase, an aceto-acetyl-CoA reductase, and a PHA synthase from R. eutropha, respectively. The btkBRe gene encodes a second 3-ketothiolase isolated from R. eutropha which shows high affinity for both propionyl-CoA and acetyl-CoA [40]. PDC refers to the endogenous plant pyruvate dehydrogenase complex...

PYRUVATE CARBOXYLASE PYRUVATE DEHYDROGENASE KINASE PYRUVATE KINASE PYRUVATE, WATER DIKINASE RESTRICTION ENZYMES RHODOPSIN KINASE RIBOFLAVIN KINASE RIBONUCLEOTIDE REDUCTASE... 

NITRATE REDUCTASE NITRITE REDUCTASE PHENOL HYDROXYLASE PROLINE DEHYDROGENASE PUTRESCINE OXIDASE PYRUVATE OXIDASE SALICYLATE 1-MONOOXYGENASE SUCCINATE DEHYDROGENASE SULFITE REDUCTASE XANTHINE OXIDASE Falling ball viscometry,... 

Fig. 3 Speculative metabolic schemes of the main pathways in carbohydrate metabolism in N. ovalis Abbreviations AcCoA, acetyl-CoA, Cl, complex I, Citr, citrate, FRD, fumarate reductase, FUM, fumarate, Hyd, hydrogenase, a-KG, a-ketoglutarate, MAL, malate, OXAC, oxaloacetate, PDH, pyruvate dehydrogenase, PEP, phosphoenolpyruvate carboxyk-inase, PYR, pyruvate, RQ, rhodoquinone, SUCC, succinate, SUCC-CoA, succinyl-CoA...

Elaborate cascades initiate the clotting of blood (Chapter 12) and the action of the protective complement system (Chapter 31). Cascades considered later in the book are involved in controlling transcription (Fig. 11-13) and in the regulation of mammalian pyruvate dehydrogenase (Eq. 17-9), 3-hydroxy-3-methyl-glutaryl-CoA reductase and eicosanoids (Chapter 21), and glutamine synthetase (Chapter 24). 

Dehydrogenases often act primarily to reduce a carbonyl compound rather than to dehydrogenate an alcohol. These enzymes may still be called dehydrogenases. For example, in the lactic acid fermentation lactate is formed by reduction of pyruvate but we still call the enzyme lactate dehydrogenase. In our bodies this enzyme functions in both directions. However, some enzymes that act mainly in the direction of reduction are called reductases. An example is aldose reductase, a member of a family of aldo-keto reductases71 73 which have (a / P)8-barrel structures.74 76... 

Fig. 20.1. Generalized scheme of the main pathways of aerobic and anaerobic carbohydrate degradation in parasitic flatworms. The aerobic pathway is indicated by open arrows, whereas the anaerobic pathway (malate dismutation) is indicated by solid arrows. Abbreviations AcCoA, acetyl-CoA ASCT, acetateisuccinate CoA-transferase C, cytochrome c CI-CIV, complexes I—IV of the respiratory chain CITR, citrate FRD, fumarate reductase FUM, fumarate MAL, malate Methylmal-CoA, methylmalonyl-CoA OXAC, oxaloacetate PEP, phosphoenolpyruvate PROP, propionate Prop-CoA, propionyl-CoA PYR, pyruvate RQ, rhodoquinone SDH, succinate dehydrogenase SUCC, succinate Succ CoA, succinyl CoA UQ, ubiquinone.

Fig. 5.4. Two types of energy metabolism in cestodes. (a) Type 1 homolactate fermentation, (b) Type 2 Malate dismutation. Reaction 3 involves a carboxylation step decarboxylation occurs at 6, 7 and 10. Reducing equivalents are generated at reactions 6 and 7 one reducing equivalent is used at reaction 9. Thus, when the mitochondrial compartment is in redox balance and malate is the sole substrate, twice as much propionate as acetate is produced. Key 1, pyruvate kinase 2, lactate dehydrogenase 3, phosphoenolpyruvate carboxykinase 4, malate dehydrogenase 5, mitochondrial membrane 6 malic enzyme 7, pyruvate dehydrogenase complex 8, fumarase 9, fumarate reductase 10, succinate decarboxylase complex. indicates reactions at which ATP is synthesised from ADP cyt, cytosol mit, mitochondrion. (After Bryant Flockhart, 1986.)...

Fig. 5.8. Respiratory pathways in Echinococcus spp., sites of ATP synthesis (ox) oxidative, and (red) reductive processes PK, pyruvate kinase OAA, oxaloacetate ME(c), ME(m), malic enzyme (cytosolic) or (mitochondrial) FR, fumarate reductase PDH, pyruvate dehydrogenase complex. (After McManus Bryant, 1986.)...

Fig. 5.2. Possible metabolic pathways in facultative anaerobic mitochondria. Shaded boxes show components of the electron-transport chain used during hypoxia, open boxes are components used during aerobiosis, and the hatched boxes (complex I and ATP-synthase) are components used under aerobic as well as anaerobic conditions. ASCT acetate succinate CoA-transferase, C cytochrome c, Cl, CIII and CIV complexes I, III and IV of the respiratory chain, CITR citrate, ECR enoyl-CoA reductase (such as present in Ascaris suum), ETF electron-transfer flavoprotein, ETF RQ OR electron-transfer flavoproteimrhodoquinone oxidoreductase, FRD fumarate reductase, FUM fumarate, MAE malate, OXAC oxaloacetate, PYR pyruvate, RQ rhodoquinone, SDH succinate dehydrogenase, SUCC succinate, Succ-CoA succinyl-CoA, TER trans-2-enoyl-CoA reductase (such as present in E. gracilis), UQ ubiquinone...

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