Diglyceride kinase in human platelets

Abstract

Human platelets contain diglyceride kinase, an enzyme that catalyzes the phosphorylation of diacylglycerol by adenosine 5′-triphosphate to yield phosphatidic acid. The majority of the platelet enzyme is particulate-bound, and membrane fractions of platelet homogenates have a higher specific activity than granule fractions. Both deoxycholate and magnesium are necessary for optimal enzyme activity. The Km of the enzyme for adenosine 5′-triphosphate is 1.3 mm, and the apparent Km for diacylglycerol is 0.4 mm. The pH optimum is 6.6–6.8 in imidazole–HCl or maleate–NaOH buffer. The enzyme activity of platelets from normal subjects was similar to the activity from patients with renal and hepatic failure.

Keywords

• 1,2-diacylglycerol
• diolein
• monoolein
• adenosine 5′-triphosphate
• phosphatidic acid
• deoxycholate