Bile salt activation of human cholesterol esterase does not require protein dimerisation.

Abstract

Human milk cholesterol esterase (bile salt-activated lipase) plays a role in the dietary uptake of triacylglyceride and cholesteryl ester. The activities toward these substrates are mediated through a unique bile salt-activated mechanism. Previously, it has been proposed that a necessary step in this process is prior protein dimerisation in the presence of primary bile salts. In this study, we addressed the role of protein dimerisation by investigating bile salt interactions on full length and truncated recombinant forms, as analysed by size exclusion chromatography and concanavalin A Sepharose binding experiments. The present findings demonstrate that protein dimerisation is not an obligatory component of the bile salt-activated pathway. A new functional role for the glycosylated C-terminal domain in cholesterol esterase is also demonstrated in the prevention of non-specific hydrophobic interactions.