Myocardial phospholipase a of microsomal and mitochondrial fractions

• Published in: Biochimica et biophysica acta Vol. 231; no. 3; pp. 512 - 519
• Main Authors: Weglicki, W.B., Waite, M., Sisson, P., Shohet, S.B.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 04.05.1971
• Subjects: Animals; Calcium; Carbon Isotopes; Cell Fractionation; Dogs; Edetic Acid; Hydrogen-Ion Concentration; Male; Membranes - enzymology; Microsomes - enzymology; Mitochondria, Muscle - enzymology; Myocardium - cytology; Myocardium - enzymology; Phosphatidylethanolamines; Phospholipases - antagonists & inhibitors; Rats; Tritium
• ISSN: 0005-2760; 0006-3002; 1879-145X
• DOI: 10.1016/0005-2760(71)90119-6

1. 1. Phospholipase A 1 and Ag 2 activities of mitochondria and microsomes of myocardial tissue have been determined using exogenous [ 14C]phosphatidyl ethanolamine and [ 14C]phosphatidyl choline. Mitochondrial phospholipase A 2 had a pH optimum of 9.5, required 2.0 mM Ca 2+ for optimal activity and was markedly inhibited by 1.0 mM EDTA. Microsomal phospholipase A 1 and A 2 activities were optimal at pH 7.5 in the presence of 2.0 mM Ca 2+ and were minimally inhibited by 1.0 mM EDTA. 2. 2. Incubations with 3H- 14C mixed labeled phosphatidyl ethanolamine further confirmed the above observations and implicated lysophospholipase activity in the microsomal fractions. 3. 3. Phosphatidyl ethanolamine was preferred to phosphatidyl choline as substrate. 4. 4. This endogenous phospholipase A activity in the microsomal membranes of the myocardium may have relevance to in vitro studies of Ca 2+ permeability and Ca 2+-dependent ATPase changes previously noted during snake venom phospholipase A treatment of muscle membranes.