Pyruvate dehydrogenase energy metabolism

Fig. 1. Energy metabolism in the normal myocardium (ATP adenosine-5 -triphosphate, ADP adenosine-5 -diphosphate, P phosphate, PDH pyruvate dehydrogenase complex, acetyl-CoA acetyl-coenzyme A, NADH and NAD" nicotinamide adenine dinucleotide (reduced and oxidized), FADH2 and FAD flavin adenine dinucleotide (reduced and oxidized).

The oxidative decarboxylation of pyruvate and a-ketoglutaraie I which plays a key role in energy metabolism of most cells, is parn ularly important in tissues of the nervous system. In thiaminel deficiency, the activity of these two dehydrogenase reactions <1 decreased, resulting in a decreased production of ATP and, fxsi I... 

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.)...

ATP plays a central role in cellular maintenance both as a chemical for biosynthesis of macromolecules and as the major soirrce of energy for all cellular metabolism. ATP is utilized in numerous biochemical reactions including the eitric acid cycle, fatty acid oxidation, gluconeogenesis, glycolysis, and pyruvate dehydrogenase. ATP also drives ion transporters sueh as Ca -ATPase in the endoplasmic reticulum and plasma membranes, H+-ATPase in the lysosomal membrane, and Na+/K+-ATPase in the plasma membrane. Chemieal energy (30.5 kJ/mol) is released by the hydrolysis of ATP to adenosine diphosphate (ADP). 

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