Are monoglyceride-lipase, triglyceride-lipase and phospholipase A of rat liver microsomes distinct protein entities?

Abstract

1. Different extraction and purification techniques were employed for the separation of MG-lipase, TG-lipase and phospholipase A from rat liver microsomes. 2. Up to 60 per cent of the microsomal content of TG-lipase and phospholipase could be extracted with 1 M KCl or NaCl. MG-lipase was extracted more readily by detergents (e.g. emulphogen). 3. MG-lipase is more resistant to detergent and heat inactivation than TG-lipase and phospholipase A. It is retained, using the technique of affinity chromatography, on a column of CH-Sepharose coupled to monooleoylglycerol. In addition, MG-lipase was separated from TG-lipase by electrofocusing. 4. TG-lipase and phospholipase A were partially separated by gel filtration on Sephadex G-200 in the presence of 1 mM dithiothreitol and by chromatography on CH-Sepharose 4b. 5. On the basis of the present extraction and purification studies, it is concluded that mg-lipase is an enzyme protein distinct from TG-lipase and phospholipase A.