Assay of nanogram levels of triglyceride lipase with a radioactive substrate.

A simple, sensitive procedure for the determination of triglyceride lipase activity has been developed. Nanogram amounts of oleic acid hydrolyzed from commercially available [(14)C]triolein were readily determined by the counting of the radioactivity of substrate and product after their rapid chromatographic separation on copper hydroxide-impregnated ion-exchange paper. Comparison of the relative amounts of radioactivity of the separated substrate and product gave an estimate of the percentage of hydrolysis of substrate. Comparison of results with a standard of pure lipase enables one to express the amount of hydrolysis in terms of the standard lipase. The results show that measured activity is a linear function of time up to 1 hr of incubation and of amounts of enzyme up to 125 ng. Reproducibility of the test is good.