MCB 2000 Lecture Notes - Lecture 24: Decarboxylation, Dehydrogenation, Oxaloacetic Acid
Document Summary
Citrate synthase: involves a condensation reaction between oaa and acetyl coa. Ordered binding: oaa induces a major structural change to create a binding site for acetyl coa. Importance of hydrolysis of high energy thioester bond. When acetyl coa comes off, means thioester bond has been split. Not much oaa is produced because it is not energetically favorable. Hydrolysis of high energy thioester bond ensures that the reaction proceeds irreversibly to the right. Free energy change favors malate (reverse reaction) Citrate is isomerize by aconite to form isocitrate. Citrate is a poor substrate for oxidation. Aconitase isomerizes citrate to yield isocitrate which has a secondary -oh which can be oxidized. Reaction involves a dehydration followed by hydration to enable an oxidative decarboxylation to occur in the next step. Rst of four redox reactions: oxidation of alcohol to keto group. Classic nad+ chemistry (hydride removal) followed by a decarboxylation. Isocitrate dehydrogenase catalyzes the rst oxidative decarboxylation in the cycle.
