Holoenzyme
Biochemically active conjugated enzyme (apoenzyme + cofactor)
A holoenzyme is a complete and active enzyme consisting of both a protein component (apoenzyme) and a non-protein component (cofactor or prosthetic group). The term holoenzyme is derived from “holo-” which means complete. The cofactor or prosthetic group can be an inorganic ion, such as Mg2+ or Fe3+, or a small organic molecule, such as NAD+ or biotin.
Cofactors or prosthetic groups often play crucial roles in the catalytic activity of enzymes. They can participate in the enzymatic reaction by acting as electron donors or acceptors, or they can provide functional groups that aid in substrate binding and catalysis. The binding of the cofactor or prosthetic group to the apoenzyme induces conformational changes that allow for the enzymatic reaction to occur.
Holoenzymes are important in many biological processes, including metabolism, DNA replication, and cellular respiration. For example, the holoenzyme DNA polymerase III is responsible for catalyzing the synthesis of new DNA strands during DNA replication. The holoenzyme ATP synthase catalyzes the synthesis of ATP from ADP and inorganic phosphate during cellular respiration.
In summary, a holoenzyme is a complete and active enzyme consisting of both a protein component and a non-protein component. The non-protein component can be a cofactor or prosthetic group that plays a crucial role in the catalytic activity of the enzyme.
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