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In contrast to the relatively facile decarboxylation of β-keto acids, the decarboxylation of α-keto acids presents a mechanistic challenge. Thiamine pyrophosphate (TPP) provides the biochemical and enzymological answer. TPP is the key catalytic cofactor used by enzymes catalyzing non-oxidative and oxidative decarboxylation of α-keto acids.
It is an oxidative carboxylase that catalyses the oxidative decarboxylation of 6-phosphogluconate into ribulose 5-phosphate in the presence of NADP. This reaction is a component of the hexose mono-phosphate shunt and pentose phosphate pathways (PPP).
This enzyme complex catalyzes the oxidative decarboxylation of branched, short-chain alpha-ketoacids. BCKDC is a member of the mitochondrial α-ketoacid dehydrogenase complex family, which also includes pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase, key enzymes that function in the Krebs cycle.
The NADH generated by the citric acid cycle is fed into the oxidative phosphorylation (electron transport) pathway. The net result of these two closely linked pathways is the oxidation of nutrients to produce usable chemical energy in the form of ATP. In eukaryotic cells, the citric acid cycle occurs in the matrix of the mitochondrion.
Pyruvate decarboxylase depends on cofactors thiamine pyrophosphate (TPP) and magnesium. This enzyme should not be mistaken for the unrelated enzyme pyruvate dehydrogenase, an oxidoreductase (EC 1.2.4.1), that catalyzes the oxidative decarboxylation of pyruvate to acetyl-CoA.
Pyruvate undergoes oxidative decarboxylation in which it loses its carboxyl group (as carbon dioxide) to form acetyl-CoA, giving off 33.5 kJ/mol of energy. The oxidative conversion of pyruvate into acetyl-CoA is referred to as the pyruvate dehydrogenase reaction. It is catalyzed by the pyruvate dehydrogenase complex. Other conversions between ...
Pyruvate decarboxylation or pyruvate oxidation, also known as the link reaction (or oxidative decarboxylation of pyruvate [1]), is the conversion of pyruvate into acetyl-CoA by the enzyme complex pyruvate dehydrogenase complex. [2] [3] The reaction may be simplified as: Pyruvate + NAD + + CoA → Acetyl-CoA + NADH + CO 2
The pentose phosphate pathway protects the trypanosomes from oxidative stress via the generation of NADPH and provides carbohydrate intermediates used in nucleotide synthesis. [12] Structural differences between mammalian and trypanosome 6-phosphogluconate dehydrogenase have allowed for the development of selective inhibitors of the enzyme.