Studies in bile salt solutions. Deoxycholate stimulation of human milk lipase.

Stimulation of human milk lipase by deoxycholate and its taurine and glycine conjugates was demonstrated by measuring the esterolysis reaction of 4-nitrophenylacetate. The steroidal surfactants did not bind strongly to the polar substrate but they did bind effectively to a hydrophobic site on the enzyme and these bile salt-enzyme complexes were effective catalysts. These results are compared with those for stimulation of the enzyme by cholate surfactants and it has been demonstrated that the absence of a 7 alpha-OH substituent on the steroid nucleus does not prevent stimulation of either the esterolytic or lipolytic activity of the enzyme.