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Concept
Décarboxylation oxydative
Résumé
Oxidative decarboxylation is a decarboxylation reaction caused by oxidation. Most are accompanied by α- Ketoglutarate α- Decarboxylation caused by dehydrogenation of hydroxyl carboxylic acids such as carbonyl carboxylic acid, malic acid, isocitric acid, etc.
Pyruvate catalytic reaction catalyzed by pyruvate dehydrogenase system is a special decarboxylation method, namely oxidative decarboxylation, which is different from the common decarboxylation reaction, namely common decarboxylation.
The oxidative decarboxylation reaction is catalyzed by pyruvate dehydrogenase system, which includes three different enzymes: pyruvate dehydrogenase (E1), dihydrolipoamide acetyltransferase (E2), dihydrolipoamide dehydrogenase (E3), and six cofactors: thiamine pyrophosphate (TPP), lipoamide, coenzyme A (CoA), flavin adenine dinucleotide (FAD), nicotinamide adenine dinucleotide (NAD+), and magnesium ion.
During the reaction, E1 participates in the decarboxylation of pyruvic acid, and then TPP connects the acetyl group after the reaction. The carbonyl group of the acetyl group reacts with the carbonyl group of the carbon negative ion on the thiazole ring of TPP to form hydroxyethyl. Then, with the catalysis of E2, TPP sends the hydroxyethyl to lipoamide, which is reoxidized to acetyl to produce thioester bond. At this time, the compound is acetyl dihydrolipoamide, which is then catalyzed by E2, and acetyl is transferred, to form acetyl CoA, all the above reactions only involve decarboxylation reaction, and do not involve the movement of H, while the real dehydrogenation effect of pyruvate dehydrogenase system will be reflected in the next step of reaction. Acetyl dihydrolipoamide without acetyl group is lost, that is, dihydrolipoamide needs to be re oxidized to lipoamide to participate in the reaction again. At this time, E3 needs to participate in the catalytic reaction, and the hydrogen removed from dihydrolipoamide will be transferred to FAD to make it FADH2, FADH2 reacts with NAD+to generate NADH and H+.
Source officielle
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