coenzymes and cofactors


coenzymes

 

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

 

 coenzymes in group transfer reactions

 coenzyme

 abbreviation

 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

 CoA

 Acyl groups

 coenzymeQ

 CoQ

 electrons (hydrogen atom)

 thiamine pyrophosphate

 thiamine (vit. B1)

 aldehydes

 pyridoxal phosphate

 pyridoxine (vit B6)

 amino groups

 biotin

 biotin

 carbon dioxide

 carbamide coenzymes

 vit. B12

 alkyl groups


cofactors 

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

 cofactor

 enzyme or protein

 Zn++

 carbonic anhydrase

 Zn++

 alcohol dehydrogenase

 Fe+++ or Fe++

 cytochromes, hemoglobin

 Fe+++ or Fe++

 ferredoxin

 Cu++ or Cu+

 cytochrome oxidase

 K+ and Mg++

 pyruvate phosphokinase


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