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Alpha-methylacyl-CoA racemase
In enzymology, an alpha-methylacyl-CoA racemase, also known as AMACR, is an enzyme that catalyzes the following chemical reaction:
:(2''R'')-2-methylacyl-CoA (2''S'')-2-methylacyl-CoA
In mammalian cells, the enzyme is responsible for converting (2''R'')-methylacyl-CoA esters to their (2''S'')-methylacyl-CoA epimers and known substrates, including coenzyme A esters of pristanic acid (mostly derived from phytanic acid, a 3-methyl branched-chain fatty acid that is abundant in the diet) and bile acids derived from cholesterol. This transformation is required in order to degrade (2''R'')-methylacyl-CoA esters by β-oxidation, which process requires the (2''S'')-epimer. The enzyme is known to be localised in peroxisomes and mitochondria, both of which are known to β-oxidize 2-methylacyl-CoA esters.〔〔
== Nomenclature ==
This enzyme belongs to the family of isomerases, specifically the racemases and epimerases which act on other compounds. The systematic name of this enzyme class is 2-methylacyl-CoA 2-epimerase. In vitro experiments with the human enzyme AMACR 1A show that both (2''S'')- and (2''R'')-methyldecanoyl-CoA esters are substrates and are converted by the enzyme with very similar efficiency. Prolonged incubation of either substrate with the enzyme establishes an equilibrium with both substrates or products present in a near 1:1 ratio. The mechanism of the enzyme requires removal of the α-proton of the 2-methylacyl-CoA to form a deprotonated intermediate (which is probably the enol or enolate〔) followed by non-sterespecific reprotonation.〔 Thus either epimer is converted into a near 1:1 mixture of both isomers upon full conversion of the substrate.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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