Proteinaceous Inhibitors of Lipase Activities in Soybean and Other Oil Seeds

Abstract

There are at least three major mechanisms whereby an inhibitor of an enzyme may exert its effect. These three mechanisms are all exemplified by lipase inhibitors. In the first mechanism, the inhibitor acts directly on the enzyme molecule, either binding to or altering it. Examples are the apolipoproteins of the lipoproteins, which modulate (activate as well as inhibit) epithelium lipase activities (Cheng et al. 1990). In the second mechanism, the inhibitor acts as a substrate analog, which exerts its effect on the active site reversibly or irreversibly. Lipase inhibitors employing this mechanism include the reversible inhibitors of alkyl and aryl boronic acid derivatives (Garner 1980), and the irreversible inhibitors of synthetic 1,6-di(O-(carbamyl)cyclohexanone oxime)hexane (Sutherland and Amin 1982) and Streptomyces toxytricini lipstatin (Borgstrom 1988; Hadvary et al. 1988). In the third mechanism, the inhibitor acts on the substrate, thereby reducing the availability of the substrate to the enzyme. It is exemplified by many artificial surfactants and amphiphatic proteins which bind to the surface of the substrate emulsion of lipase (Ransac et al. 1990).