STUDY OF RAT-LIVER PLASMA-MEMBRANES PHOSPHOLIPASE-A

  • 1 January 1975
    • journal article
    • research article
    • Vol. 57  (10) , 1221-1227
Abstract
The plasma membranes phospholipase A2 studied in situ shows very little sensitivity for pH variations; the optimal concentration for Ca2+ is 5 mM; the enzymatic kinetics are of the Michaelis type. An inactive state of the phospholipase A2 exists: when rats are injected with heparin, their plasma membranes contain a very low phospholipase A2 activity. These membranes recover a high A2 activity if they are incubated in the presence of a rat platelets lysate. Treatment of membranes by NaCl 1 M displaces phospholipase A1 and phospholipase A2 but for the latter only when being in active state. Treatment of animals, conditions of preparation and of incubation of membranes influence the respective amounts of phospholipases A1 and A2 present in these membranes and are discussed in this paper. The localization of these enzymatic proteins inside the membrane according to the membranous model proposed by Singer et al. is also discussed.