Abstract
The activity of sterol ester hydrolase was found in the crude enzyme preparation of lipoprotein lipase from Pseudomonas fluorescence. The enzyme was purified by ammonium sulfate fractionation and chromatographies on diethylaminoethyl (DEAE)-cellulose, Sephadex G-75 and carboxymethyl (CM)-cellulose. The lipolytic activity and sterol ester hydrolytic activity at various stages in the purification were found in the same fraction and the ratio of both activities was constant. The purified enzyme was found to be homogeneous by disc electrophoresis and SDS-polyacrylamide gel electrophoresis. Furthermore, one single protein peak which contained lipolytic and sterol ester hydrolytic activities was observed by isoelectric focusing. Therefore, it was concluded that the actions of lipoprotein lipase and sterol ester hydrolase will belong to a same enzyme protein. The action of the purified enzyme for the cholesterol esters in human plasma was investigated. Cholesterol ester was hydrolyzed completely and the rate of hydrolysis of esters of long chain fatty acids was more rapid than that of short.
