Answer to Question #28476 in Biochemistry for ahmad alnaely

Question

1.show the oxidation/reduction reactions that are catalyzed by isocitrate dehydrogenase in the Citric Acid cycle.
2.identify the coenzyme that is reduced concurrently with oxidative-decarboxylation of pyruvate

Answer 1

1. Isocitrate Dehydrogenase
Two events occur in this reaction of the citric acid cycle. In the first reaction, we see our first generation of NADH from NAD. The enzyme isocitrate dehydrogenase catalyzes the oxidation of the –OH group at the 4' position of isocitrate to yield an intermediate which then has a carbon dioxide molecule removed from it to yield alpha-ketoglutarate.

isocitrate + NAD = intermediate + NADH
intermediate = alpha-ketoglutarate + CO₂

2. Pyruvate ------> Acetyl-CoA + CO₂
Multi-enzyme complex, the intermediates remain bound to the enzyme. Enzyme channeling. Overall reaction is irreversible, a REDOX Reaction. OXID: Pyruvate ------> Acetyl-CoA
RED: NAD⁺ ------> NADH
Coenzyme-A: Has a reactive Thiol (SH) group. When acyl groups get hooked on (i.e. acetyl), they form a thioester with very high free energies of hydrolysis.