Purification of rat liver mevalonate pyrophosphate decarboxylase

Mevalonate pyrophosphate decarboxylase was isolated from rat liver to 90% purity as judged by SDS-PAGE using Phenyl Sepharose, p-coumaric acid-Sepharose, Mono P, and Mono Q chromatography. Gel filtration chromatography of the crude extract determined the native enzyme to be near 100 kDa while SDS-PAGE of the purified enzyme showed a protein band at 45 kDa. This implies that the native rat liver enzyme is a homodimer which differs from the published report that the enzyme is a tetramer of 35 kDa subunits. We measured a specific activity of 4.6 units/mg and a KM for mevalonate pyrophosphate of 20 microM. These values are similar to those reported for the chicken liver and the pig liver enzymes, but differ from the published report of the rat liver enzyme.