Interfacial catalysis by lipases'

We designed a convenient, specific, sensitive and continuous lipase activit y assay using natural long-chain triacylglycerols (TAGs). Oil was extracted from Parinari glaberrimum seed kernels and the purified TAGs used as a sub strate for detecting low levels of lipase activities. The purified TAGs are naturally fluorescent. The presence of detergents above their critical mic ellar concentration dramatically increases the fluorescence of the parinari c acid released by various lipases, This increase is linear with time and p roportional to the amount of lipase added. Quantities as low as 0.1 ng of p ure pancreatic lipase could be detected under standard conditions (pH 8), The interfacial activation of human pancreatic lipase (HPL) probably involv es the motion of a lid covering the active site of the enzyme. We observed that the presence of either bile salts or a small proportion of water-misci ble organic solvents (called activator compounds) considerably enhances the enzymatic activity of HPL on a monomeric solution of tripropionin. This fi nding suggests that the activator compounds may favor the opening of the li d, This hypothesis was checked by comparing the immunoreactivity of HPL and HPL with a mini-lid (HPL(-lid)) towards anti-HPL monoclonal antibodies (mA bs), in the presence and absence of the activator compounds. (C) 2001 Elsev ier Science B.V. All rights reserved.