Essential fatty acids pyruvate dehydrogenase

IMPLICATION OF ESSENTIAL FATTY ACIDS IN PYRUVATE DEHYDROGENASE ACTIVATION... 

The liver and kidney cortex have a unique role in gluconeogenesisconverting pyruvate to glucose. Some of the controls are bifunctional, for example, the increased acetyl CoA in the liver from fatty-acid metabolism will not only inhibit pyruvate dehydrogenase but also activate pyruvate carboxylase, where acetyl CoA is an essential activator (Fig. 13.2). 

Several of the B vitamins are essential for normal fatty-acid metabolism (Table 2). Pantothenic acid is a constituent of CoA and is thus required for numerous reactions of fatty acids. Niacin and riboflavin are necessary for the synthesis of oxidized and reduced NAD(P) and FAD, respectively. These compounds play essential roles in fatty-acid oxidation, synthesis, and elongation. Biotin is a constituent of acetyl-CoA carboxylase and pyruvate carboxylase, both of which are involved in the synthesis of fatty acids from glucose. Thiamine is required for activity of the pyruvate dehydrogenase complex, which also participates in fatty-acid synthesis from glucose. 

Two important reactions involving coenzyme A are worthy of mention the first is the oxidative decarboxylation of pyruvate to acetyl-coenzyme A, which is catalyzed by the multienzyme complex, pyruvate dehydrogenase. This reaction involves a series of steps mediated by five coenzymes, during which a series of acid-base reactions and nucleophilic displacements take place, with pyruvate being oxidized and converted to acetyl-CoA. Another essential series of reactions involving acetyl-CoA is that of fatty acid synthesis. Here acetyl-CoA is converted to malonyl-CoA through condensation of the enzyme-bound thioester, with the occurrence of simultaneous decarboxylation. 

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