Diphosphomevalonate decarboxylase (EC 4.1.1.33), most commonly referred to in scientific literature as mevalonate diphosphate decarboxylase[citation needed], is an enzyme that catalyzes the chemical reaction This enzyme converts mevalonate 5-diphosphate (MVAPP) to isopentenyl diphosphate (IPP) through ATP dependent decarboxylation.

An aspartic acid residue deprotonates the C3 hydroxyl on MVAPP and facilitates the oxygen to attack a phosphate from ATP.

Though there is limited information, some important residues have been identified and are highlighted in the active site structure and mechanism.

[1] Asp-305 is positioned about 4 Å from the C3 hydroxyl on MVAPP and acts as a general base catalyst in the active site.

[1] Mevalonate diphosphate decarboxylase also has a phosphate-binding loop (‘P-loop’) where amino acid residues provide key interactions that stabilize the nucleotide triphosphoryl moiety.

[10] The main point of regulation in cholesterol and nonsterol isoprene biosynethsis is HMGCoA reductase, the third enzyme in the mevalonate pathway.

[12] Hypercholesterolemia or high cholesterol is considered a major risk factor in coronary artery disease.

[14][15] In humans, it is hypothesized that cholesterol deficiency may make the plasma membranes fragile and, as a result, induce angionecrosis in the brain.

Reduced serum cholesterol, resulting from a low activity of mevalonate diphosphate decarboxylase, may be the cause of cerebral hemorrhage in some cases.