Studies on heat stability of phospholipase A2 in human serum

Heat stability of human serum phospholipase A2 (PLA2) was investigated comparing to those of porcine pancreatic PLA2 (p-PLA2) and PLA2 in human duodenal aspirate. PLA2 activity was measured by radiochemical method using phosphatidylcholine as a substrate. While the activities of PLA2 in duodenal aspirate and p-PLA2 solution were not influenced by the heat treatment of 55°C, PLA2 activity in normal human serum was remarkably decreased by the preincubation at 55°C for only 5 minutes. From the result of preincubation temperature, serum PLA2 activity began to decrease at 50°C and the decrease of PLA2 activity was remarkable above 55°C of preincubation temperature. As a conclusion, PLA2 in human serum was consisted of heat labile and stable form, and latter was thought to be derived from pancreas. Thus serum PLA2 level should be assessed with consideration of incubation temperature of PLA2 assay and whether pretreatment of heating was done or not.