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The non-protein chemical compound or metallic ion that is required for an enzyme's activity as a catalyst is known as a cofactor. It is a substance that increases the rate of a chemical reaction. Cofactors can be considered "helper molecules" that help in biochemical transformations. When an enzyme requires a cofactor for its activity, the inactive protein component is generally referred to as an apoenzyme, and the apoenzyme plus the cofactor is called a holoenzyme.

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