Mechanism of inhibition of hepatic triglyceride lipase from human postheparin plasma by apolipoproteins A-I and A-II.

The present data describe the mechanism of the inhibitory effects of human plasma apolipoproteins A-I and A-II on hydrolysis of triglyceride catalyzed by hepatic triglyceride lipase using a substrate of triolein particles stabilized with gum arabic in vitro. The experimental data could well be described by a model in which apolipoproteins bound to the surface of lipid substrate particles inhibited the enzyme reaction. The values of Km obtained were similar with or without inhibitors and the calculated saturation levels of apolipoprotein binding to the lipid were in good agreement with those obtained in independent binding experiments.