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Usually, decarboxylation refers to a reaction of carboxylic acids, removing a carbon atom from a carbon chain. The reverse process, which is the first chemical step in photosynthesis , is called carboxylation , the addition of CO 2 to a compound.
These enzymes catalyze the decarboxylation of amino acids and alpha-keto acids. [1] Classification and nomenclature
The enzyme is necessary to help the decarboxylation of alpha-keto acids because there is a build-up of negative charge that occurs on the carbonyl carbon atom in the transition state; therefore, the enzyme provides the suitable environment for TPP and the alpha-keto acid (pyruvate) to meet. [4]
In animal tissue, BCKDC catalyzes an irreversible step [2] in the catabolism of the branched-chain amino acids L-isoleucine, L-valine, and L-leucine, acting on their deaminated derivatives (L-alpha-keto-beta-methylvalerate, alpha-ketoisovalerate, and alpha-ketoisocaproate, respectively) and converting them [3] to α-Methylbutyryl-CoA, Isobutyryl-CoA and Isovaleryl-CoA respectively.
Pyruvate decarboxylation is also known as the "pyruvate dehydrogenase reaction" because it also involves the oxidation of pyruvate. [ 2 ] This multi-enzyme complex is related structurally and functionally to the oxoglutarate dehydrogenase and branched-chain oxo-acid dehydrogenase multi-enzyme complexes.
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 process consumes a proton in the decarboxylation and employs a pyridoxal-5'-phosphate (PLP) cofactor, similar to other enzymes involved in amino acid metabolism, such as ornithine decarboxylase and glutamine decarboxylase. [1] It is found in bacteria and virus, though most research has so far focused on forms of the enzyme in bacteria.
The enzyme ornithine decarboxylase (EC 4.1.1.17, ODC) catalyzes the decarboxylation of ornithine (a product of the urea cycle) to form putrescine. This reaction is the committed step in polyamine synthesis. [1] In humans, this protein has 461 amino acids and forms a homodimer. [2] In humans, ornithine decarboxylase (ODC) is expressed by the ...