The Effects of O- and N-Linked Glycosylation on the Secretion and Bile Salt-Stimulation of Pancreatic Carboxyl Ester Lipase Activity

Abstract

Pancreatic carboxyl ester lipase is a glycoprotein that requires millimolar concentrations of trihydroxy bile salts, such as cholate, for maximal catalytic activity against cholesteryl esters and triglycerides. Binding of cholate, with subsequent activation, has been proposed to occur in the carboxy-terminal region of carboxyl ester lipase, which contains multiple sites for O-linked glycosylation (1). To investigate the role of O- and N-linked glycosylation in the secretion of carboxyl ester lipase by cells and its activation by cholate, rat carboxyl ester lipase cDNA was transfected into the mutant chinese hamster ovary cell line, IdID, and the ability of the cells to modify the expressed carboxyl ester lipase by N- and O-linked glycosylation was modulated by using various incubation conditions and metabolic inhibitors. The results showed that, similar to other lipases, maximal secretion of carboxyl ester lipase activity required N-linked glycosylation. In contrast, O-linked glycosylation did not affect the secretion of carboxyl ester lipase activity. In addition, the cholate stimulation of hydrolysis was also independent of O-linked glycosylation.