大動脈壁中の脂質分解酵素について

Abstract

In order to clarify a part of lipid metabolism in aortic wall, the properties of lipolytic enzymes in the human aortic intima and media have been studied. Human intima and media were homogenized in ice-cold 0.01M phosphate buffer, pH7.0, and the supernatant of homogenate was used as the enzyme source.With cholesterol ester hydrolase, phospholipase and lipase in aortic intima and media, two pH optima of acid and alkaline ranges were consistently observed. In the cases of cholesterol ester hydrolase and lipase, the activities of intimal enzymes were significantly higher than those of medial ones at all pH values. On the contrary, the activity of intimal phospholipase was slightly lower than that of medial one.Comparing with the phospholipases of pancreatic juice, snake venom and starfish, the enzyme of aortic wall was unstable for heat.Alkaline lipases of intima and media were activated by sodium deoxycholate and were slightly inhibited by albumin. On the other hand, both acid lipases were not influenced by these compounds. 1M sodium chloride and protamine sulphate significantly inhibited the activity of the intimal alkaline lipase, but had no effect on the medial alkaline lipase and both the acid lipases. Heparin in low concentration slightly increased the activities of both alkaline lipases, but that of the intimal lipase was inhibited by higher concentration of heparin. These observations lead us to speculate that the main part of the intimal lipase might be lipoprotein lipase, and the medial alkaline lipase might be true lipase. The intimal alkaline lipase had the absolute positional specificity for the primary ester bond of triglyceride. On the contrary, the other lipases had the relative specificities for the primary ester bonds.