Purification and Characterization of Membrane-Bound Phospholipase A2 from Rat Platelets1

Abstract

Phospholipase A₂ was solubilized from rat platelet membrane by 1 M KC1 and purified to near homogeneity on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and HPLC. The characteristics of the purified membrane-bound enzyme were compared with those of phospholipase A₂ released from thrombin-stimulated rat platelets (Horigome, K., Hayakawa, M., Inoue, K., & Nojima, S. (1987) J. Biochem. 101, 625–631). The molecular weights, elution profiles on reversed-phase HPLC, and NH₂-terminal sequences were identical for the two enzymes. Other characteristics of the two enzymes, such as specific activity, substrate specificity, pH optimum, Ca²⁺ requirement, heat lability, and sensitivity to p-bromophenacyl bromide were also indistinguishable. These findings suggest that both enzymes share a common structure.