A-ketoglutaric dehydrogenase and

B, Thiamin Coenzyme in pyruvate and a-ketoglutarate, dehydrogenases, and transketolase poorly defined function in nerve conduction Peripheral nerve damage (beriberi) or central nervous system lesions (Wernicke-Korsakoff syndrome)... 

Thiamine pyrophosphate Is an essential coenzyme for several critical metabolic enzymes—PDH, a-ketoglutarate dehydrogenase, and transketolase of the pentose phosphate pathway. 

Krebs cycle is inhibited at the points where a-ketoglutarate dehydrogenase and succinate dehydrogenase operate. This causes an increase in organic acids and an accumulation of glutamate. 

FIGURE 16-14 Biosynthetic precursors produced by an incomplete citric acid cycle in anaerobic bacteria. These anaerobes lack a-ketoglutarate dehydrogenase and therefore cannot carry out the complete citric acid cycle. a-Ketoglutarate and succinyl-CoA serve as precursors in a variety of biosynthetic pathways. (See Fig. 16-13 for the "normal" direction of these reactions in the citric acid cycle.)... 

Other researchers had found that arsenate (AsOf ) inhibits a-ketoglutarate dehydrogenase and that malonate inhibits succinate dehydrogenase. 

Four of the Krebs cycle reactions are considered irreversible citrate synthase, isocitrate dehydrogenase, a-ketoglutarate dehydrogenase, and succinyl-CoA synthase. In two of these, COz is evolved. In one reaction, succinyl-CoA synthase, a substrate-level phosphorylation takes place, in which a high-energy compound, GTP, is generated. Note that in three of the reactions NADH is... 

Niacin is utilized in the synthesis of the nicotinamide portion of NAD, which is used in the isocitrate dehydrogenase, a-ketoglutarate dehydrogenase, and malate dehydrogenase reactions. 

Understand the role of TPP in a-ketoglutarate dehydrogenase and the role of TPP in transketolase in pentose phosphate pathway. 

Figure 15-2. The catalytic mechanism shared by the enzymes pyruvate dehydrogenase, a-ketoglutarate dehydrogenase, and branched-chain a-ketoacid dehydrogenase. E is the dehydrogenase complex E is the dihydrohpoyl transacetylase subunit, and Ej is the dihydrolipoyl dehydrogenase component. Ej and E are specific to each enzyme, and Ej is common to all three enzymes.

In Al Martini s heart failure, which is caused by a dietary deficiency of the vitamin thiamine, pyruvate dehydrogenase, a-ketoglutarate dehydrogenase, and the branched chain a-keto acid dehydrogenase complexes are less functional than normal. Because heart muscle, skeletal muscle, and nervous tissue have a high rate of ATP production from the NADH produced by the oxidation of pyruvate to acetyl CoA and of acetyl CoA to COj in the TCA cycle, these tissues present with the most obvious signs of thiamine deficiency. 

Isocitrate dehydrogenase, a-ketoglutarate dehydrogenase, and succinyl-CoA synthetase. 

Figure 29.1 shows that the high ratio of NADH NAD in the mitochondrion favours reduction of oxaloacetate to malate in the malate dehydrogenase reaction. It also restricts oxidation in the a-ketoglutarate dehydrogenase and isocitrate dehydrogenase reactions. The result is that Krebs cycle is inhibited. 

TDP is a coenzyme for many enzymes including pyruvate dehydrogenase, a-ketoglutarate dehydrogenase and transketolase where it catalyses the reversible cleavage of a substrate compound at a carbon arbon bond. 

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