Abstract
The determination and characteristics of postheparin lipolytic activities, particularly monoglyceride hydrolase and triglyceride lipase, which played the major role in the removal of neutral lipids from the general circulation, were investigated.
When the low concentration of Triton X-100 was used as emulsifier in the assay medium, it could be measured the high activity of monoglyceride hydrolase.
The pH optimum of monoglyceride hydrolase in post-heparin human plasma was 9.0. This enzyme yielded a linear rate of release of glycerol from Triton X-100-stabilized monoolein emulsions at least 90min at 37°C. Although lipoprotein lipase was inhibited with higher concentration of NaCl, monoglyceride hydrolase was slightly activated with it. About 40% of lipoprotein lipase activity was lost during the pre-incubation for 30min at 37°C. However, monoglyceride hydrolase activity was completely stable at 37°C.
In order to investigate the origin of post-heparin plasma monoglyceride hydrolase, slices from rat tissues were incubated with or without heparin. Results of these experiments suggested that the post-heparin monoglyceride hydrolase was mainly of liver origin.
In clinical studies, lipoprotein lipase and monoglyceride hydrolase activities of hyperlipemic patients, who were classified according to the criteria of WHO, were determined and compared to those of the young and aged controls.
