Coenzyme

Article By:

McCann, Mary B. Nutrition Program, Centers for Disease Control and Prevention, Health Services and Mental Health Administration, U.S. Department of Health, Education and Welfare, Rockville, Maryland.

Last reviewed:November 2019

DOI:https://doi.org/10.1036/1097-8542.146400

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• Coenzyme, published June 2014:Download PDF Get Adobe Acrobat Reader

An organic cofactor or prosthetic group (nonprotein portion of the enzyme) whose presence is required for the activity of many enzymes. Coenzymes are organic molecules that help enzymes to catalyze chemical reactions (see illustration); that is, coenzymes are required by certain enzymes in order to carry out catalysis. In addition, many enzymes need metal ions, such as copper, manganese, and magnesium, for activation. The prosthetic groups attached to the protein of the enzyme (the apoenzyme) may be regarded as dissociable portions of conjugated proteins. The coenzymes usually contain vitamins as part of their structure. Neither the apoenzyme nor the coenzyme moieties can function singly because dissociation of the two results in inactivation. In general, the coenzymes function as acceptors of electrons or functional groupings, such as the carboxyl groups in α-keto acids, which are removed from the substrate. See also: Biochemistry; Catalysis and catalysts; Enzyme; Protein; Vitamin

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