Hydrolysis of supported pyrenephospholipid monolayers by phospholipase A 2

Abstract

Hydrolysis by pancreatic and snake venom ( Crotalus atrox) phospholipase A 2 of fluorescent monolayers of pyrene-labelled phosphatidylglycerol on solid support was studied. We used a fluorescence microscope equipped with video camera, video recorder and an image analyzer to monitor changes in fluorescence. Decrease in pyrene excimer emission was evident when pyrene phosphatidylglycerol monolayers transferred onto quartz glass slides (at a surface pressure of 15 mN m −1) were subjected to enzymatic hydrolysis. Snake venom phospholipase A 2 could hydrolyze the monolayers almost completely while pancreatic phospholipase A 2 could cause only 50% decrease in fluorescence intensity. EDTA totally inhibited the action of both A 2 phospholipases. When monolayers were transferred onto solid supports at a surface pressure of 31 mN m −1 C. atrox phospholipase A 2 could still exert activity whereas porcine pancreatic phospholipase A 2 was inactive.