Pig liver phosphomevalonate kinase: kinetic mechanism.
Phosphomevalonate kinase catalyzes the phosphorylation of phosphomevalonate to diphosphomevalonate by ATP, one of the initial steps in the biosynthesis of steroids and isoprenoids. In previous studies, the enzyme from pig liver was purified and characterized, and preliminary work showed that the enzyme follows hyperbolic kinetics and a sequential mechanism. The present work is a more detailed analysis of its kinetic mechanism, using initial velocity and isotope exchange at equilibrium measurements. The results are compatible with a Bi Bi sequential ordered mechanism with phosphomevalonate as the first substrate and ADP the last product. The Km values estimated are 43+/-7 microM for Mg-ATP and 12+/-3 microM for phosphomevalonate, with a Vmax of 51+/-2 micromol min-1 mg of protein-1.
Eyzaguirre
Jaime
J
Laboratorio de Bioquímica, Pontificia Universidad Católica de Chile, Santiago, Chile. jeyzaguirre@unab.cl
Valdebenito
David
D
Cardemil
Emilio
E
D000244:Adenosine Diphosphate / Q000737:chemistry; D000255:Adenosine Triphosphate / Q000737:chemistry; D000818:Animals; D002250:Carbon Radioisotopes; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008798:Mevalonic Acid / Q000031:analogs & derivatives* / Q000737:chemistry; D010766:Phosphorylation; D017856:Phosphotransferases (Phosphate Group Acceptor) / Q000737:chemistry*; D013552:Swine
D002250:Carbon Radioisotopes; C045038:phosphomevalonic acid; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D017856:Phosphotransferases (Phosphate Group Acceptor); C022371:phosphomevalonate kinase; D008798:Mevalonic Acid