Heme groups cofactors specific enzymes

Some enzymes require cofactors for the activities Enzymes that require covalent cofactors (prosthetic groups, e.g., heme in cytochromes) or non-covalent cofactors (coenzymes, e.g., NAD(P)+ in dehydrogenases) for activities are called haloenzymes (or simply enzymes). The protein molecule of a haloenzyme is termed proenzyme. The prosthetic group/coenzyme dictates the reaction type catalyzed by the enzyme, and the proenzyme determines the substrate specificity. 

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