coenzymes and cofactors



some coenzymes and the reactions they are involved in are shown in the following table.


 coenzymes in group transfer reactions



 entity transfered

 nicotine adenine dinucelotide

 NAD - partly composed of niacin

 electron (hydrogen atom)

 nicotine adenine dinucelotide phosphate

 NADP -Partly composed of niacin

 electron (hydrogen atom)

 flavine adenine dinucelotide

 FAD - Partly composed of riboflavin (vit. B2)

 electron (hydrogen atom)

 coenzyme A


 Acyl groups



 electrons (hydrogen atom)

 thiamine pyrophosphate

 thiamine (vit. B1)


 pyridoxal phosphate

 pyridoxine (vit B6)

 amino groups



 carbon dioxide

 carbamide coenzymes

 vit. B12

 alkyl groups


Cofactors are often classified as inorganic substances that are required for, or increase the rate of, catalysis.

Examples of some enzymes that require metal ions as cofactors is shown in the table below


 enzyme or protein


 carbonic anhydrase


 alcohol dehydrogenase

 Fe+++ or Fe++

 cytochromes, hemoglobin

 Fe+++ or Fe++


 Cu++ or Cu+

 cytochrome oxidase

 K+ and Mg++

 pyruvate phosphokinase

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