The effect of surface-active agents on pancreatic lipase.

It has been known for a considerable time, e.g. Rachford (1891), that the addition of bile salts increases the rate of hydrolysis of fat by pancreatic lipase. Bile salts could speed up the rate of hydrolysis by activating the enzyme molecule, but since they are surface-active agents and therefore emulsifying agents it is clear that their activating effect could be simply due to an emulsification of the fatty substrate. A dual role is also possible, i.e. a combination of activation and emulsification. Evidence available in the literature describing the mode of action of the bile salts does not give conclusive support for either the emulsification or the activation hypothesis. Thus, Willstatter, Waldschmidt-Leitz & Memmen (1923) and Willstatter & Memmen (1924) studied the activation of lipase by bile salt and observed that some crude lipase preparations could not be activated. Further, addition ofovalbumin and Ca2+ increased the rate of fat hydrolysis so that further activation by bile salts was sometimes impossible. Bile salts were found to activate lipase in an alkaline medium but to inhibit it in an acid medium. Weinstein & Wynne (1936) found that bile salts, at pH 7-2 and in concentrations 0 5-4 x 10-4M, had no effect on the action of lipase. Glick & King (1932) found that the hydrolysis of tributyrin at pH 7-0 was inhibited by sodium taurocholate and sodium glycocholate but that the hydrolysis of triolein was accelerated. Holwerda (1938) concluded that sodium glycocholate promoted adsorption ofthe lipase on the fat. Krahling & Weber (1938) stated that bile salts affect the rate of hydrolysis of water-soluble esters by pancreatic lipase without affecting the enzymesubstrate affinity. It was considered that the use of some synthetic detergents which aid fat emulsification would help to establish the significance of the role of emulsification in the digestion of fats by lipase. The emulsification theory would, for example, be strongly supported if it were found that the synthetic detergents, which are very unlikely to be enzyme activators, stimulate lipase action. A secondary object of the investigation was to establish whether these synthetic detergents, which are representative of those widely used industrially and domestically, had any marked inhibitory effect on the action of