Coenzyme A


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coenzyme A

[kō′en‚zīm ′ā]
(biochemistry)
C21H36O16N7P3S A coenzyme in all living cells; required by certain condensing enzymes to act in acetyl or other acyl-group transfer and in fatty-acid metabolism. Abbreviated CoA.

Coenzyme A

 

(CoA), an acetylation (or acylation) coenzyme; the most important of the coenzymes.

Coenzyme A takes part in reactions involving the transfer of acyl groups. A molecule CoA consists of an adenylic acid radical (1) bonded by a pyrophosphate group (2) to a pantothenic acid radical (3) that is, in turn, linked by a peptide bond to (4) a β-mercaptoethanolamine radical (see Figure 1).

An extensive group of biochemical reactions involve CoA activity; these include the reactions at the basis of the oxidation and synthesis of fatty acids, the biosynthesis of lipids, and the oxidative conversions of the products of carbohydrate decomposition. In all cases, CoA acts as an intermediate compound, bonding the acid residues and transferring them to other substances. During this process, the acid residues either undergo

Figure 1. Coenzyme A

conversions in compounds with CoA or transfer without alteration to specific metabolites. Acyl radicals joined to the sulfhydryl (SH) group of CoA by a high-energy acylthioether bond are referred to as the active form of organic acids.

F. Lipmann, who isolated CoA from pigeon’s liver in 1947, and F. Lynen have been central in the investigation of the chemical structure and biological role of CoA. H. G. Khorana synthe-sized CoA completely in 1961.

IU. N. LEIKIN