The action of bile salts and other detergents on pancreatic lipase and the interaction with colipase

Abstract

The effect of inhibiting pancreatic lipase seems to be a property common to most detergents irrespective of charge and structure. Inhibition has no absolute relation to the critical micellar concentration (CMC) of the detergent; for most anionic detergents, inhibition is complete in the CMC range; for cationic and nonionic detergents, inhibition occurs generally at concentrations well below the CMC. Lipase inhibition occurs parallel to a displacement of lipase from the substrate interface to the aqueous phase and most probably is a general detergent effect caused by a competition at the substrate interface for hydrophobic interactions. Bile salts inhibit also the activity of lipase against “water soluble” substrates. These interactions may still be interfacial. Colipase restores lipase activity when inhibited also by detergents other than bile salts. For most other detergents this effect is, however, limited to a narrow concentration range, above which inhibition occurs also in the presence of colipase. At low detergent concentration, a lag phase τ is seen before maximal lipase activity is obtained. τ is most probably a reflection of the time needed for lipase to bind to the substrate; detergent present at the substrate interface makes this binding difficult and finally prevents it. A similar effect is seen at super-micellar detergent concentrations in the presence of colipase and the lag phase is gradually abolished by the presence of increasing concentrations of colipase parallel to an increase in lipase activity. Nonionic detergents in contrast to anionic and cationic detergents do not bind to lipase or colipase.