Biochemistry

н-с-н I соон Н.О ft H 2 O соон 1 сн, I 2 с- соон II сн I соон н,о соон I снон I н — с- соон I н — с — н I соон Citrate Cisaconitic acid Isocitrate (isocitric acid) The third reaction is isonic acid, it oxidized by splitting of two hydrogen atoms and is converted to oxalicsuccinic acid, which is decarboxylated toa- ketoglutaric acid (a-ketaglutarate). роон c=o I нс — COOH COOH I c=o I CH } I СООН I CHOH + NADCNADP) нс — соон --------- I - nadhjnadp H j ) CH, CH 2 I 2 I соон COOH Isocitrate Oxalicsuccinic acid COOH a-Ketaglutarate (a-ketoglutaric acid) a-ketoglutaric acid undergoes oxidative decarboxylation under the influence of complex enzymes (fourth reaction). The composition of these enzymes includes coenzymes (TPP, HSCoA, lipoic acid, NAD, FAD). The reaction also requires Mg" ions. As a result of the oxidative decarboxylation of a-ketoglutaric acid, succinyl- CoA is formed, which has a macroergic carboxy-thiol bond, in which the energy of oxidative decarboxylation is reserved. In this case, the second molecule CO 2 and NADH 2 is released. COOH 1 c=o + TPP.LA . HSCoA,NAD. //* C~SCoA 1 CH, | 2 -COj.NAD.H3 * 1 CH, 1 J CH 2 1 COOH COOH a-Ketoglutarate Succinyl-CoA 229