BMCB 658 Lecture Notes - Lecture 17: Succinic Acid, Oxidative Decarboxylation, Fumarase
19 Aug 2016
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Three advantages: decrease distance, increase collision frequency, channeling minimize side reactions, coordinate regulatory control. Regulation of pyruvate dehydrogenase: product inhibition: nadh & acetyl-coa, complete with nad+ & coa binding sites b. Increase in nadh or acetyl-coa drives reactions backwards: covalent phosphorylation of pdh, nadh & acetyl-coa activate pdh kinase inactive pdh b. Oxidized forms of arsenic: arsenite & organic arsenicals. Pyrvuate moves from cytosol to mitochondria via specific transporter. Final step oxaloacetate formed which can react with acetyl-coa to start the cycle again. First acetyl-coa + oxaloacetate condense to form citryl-coa. Cirtyl-coa is hydrolyzed to form citrate + coa-sh. Enzyme: citrate synthase: homodimer; each subunit has active site, oxaloacetate & acetyl-coa bind, small lobe makes 18 rotation. Tcac step 2: isomerization of citrate to isocitrate. Citrate (achiral) is converted to isocitrate (chiral) by aconitase: happens in two steps: dehydration to aconitate, then rehydration to isocitrate. Isocitrate has two stereocenters four stereoisomers possible.
