A comparative study of serum phospholipase A2 in man and animals--some biochemical and physiological implications
Singh, C.; Ramesh, V.; Anjaneyulu, K.
Indian Journal of Experimental Biology 17(1): 50-57
1979
ISSN/ISBN: 0019-5189 PMID: 112047 Document Number: 147144
A reproducible and sensitive method was employed for the assay of PLA2 (phospholipase A2 EC 3.1.1.4) activity in sera of man and 8 animal species. The method differentiated between PLA2 and PLA1 (EC 3.1.1.32) and utilized phosphatidylcholine or phosphatidylethanolamine as substrate labeled in position 2 with linoleic acid (1-14C or U-14C). The sera of man, dog, monkey, mouse, goat, sheep, and guinea pig exhibited very poor or no PLA2 activity over a wide range of pH. Some enzyme activity could be rendered perceptible by increasing the incubation time or by incorporation of Ca2+ or Hg2+ in the reaction mixture; the last measure was more effective. Trypsin pre-treatment of sera failed to reveal enzyme activity in all except human sera. Very strong enzyme activity was observed in diluted sera of rabbit, albino rat and 2 human patients (pancreatitis and malignant hypertension, MH); the activity decreased in the order rabbit > rat > pancreatitis patient > MH patient. The enzyme(s) from the 4 sources differed in their pH optima and response to Ca2+ and Hg2+. All sera studied were devoid of PLA1 activity. The rat serum enzyme was inhibited by several antioxidants, detergents, Hg2+, methanol, ether, heparin and Hb, thereby differing from PLA2 from other sources. The biological/biochemcial implications of the above are discussed.