Pig liver phosphomevalonate kinase. 1. Purification and properties

Publisher Website
Google Scholar
Abstract
Pig liver phosphomevalonate kinase (EC 2.7.4.2) was purified to homogeneity as shown by polyacrylamide gel electrophoresis. The MW estimates range from 21,000 to 22,500. Each molecule is composed of 1 polypeptide chain. The presence of SH-containing reagents is essential for preservation of enzyme activity at all steps in the purification. The enzyme shows absolute specificity for ATP and requires for activity a divalent metal cation, Mg2+ being most effective. The optimum pH for the enzyme ranges from 7.5 to over 9.5. Kinetics are hyperbolic for both substrates, showing a sequential mechanism; true Km values of 0.075 mM and 0.46 mM were obtained for phosphomevalonate and ATP, respectively. Amino acid composition shows a high content of acid amino acids, 1 cysteine residue/molecule of enzyme, and the absence of methionine. The enzyme apparently plays no regulatory function is cholesterol biosynthesis in pig liver, although a variable enzyme content was detected in different livers.