Proteins and Enzymes

ID #1499

I was just reading about how some enzymes require cofactors to operate, and I was just wondering if Heme is such a molecule. I remember learning something very vague about how some enzymes have a Heme group, and when I skimmed over this in the MCB book, it caught my attention.

The definitions get a little tricky sometimes. Cofactors are often prosthetic groups attached to enzymes to help the enzyme function. And heme is a very common prosthetic group, which would perhaps imply that heme is a cofactor. But here are a couple of important related concepts: 1) not all proteins are enzymes, and 2) not all prosthetic groups are cofactors.

So it is possible to have a prosthetic group attached to a protein, where the protein isn't an enzyme, so the prosthetic group isn't facilitating any enzymatic reaction. Such is the case with heme. Heme groups are widespread and important, but the type of heme we're most familiar with is part of a transport protein (hemoglobin), not an enzyme.

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