Bile-Salt-Stimulated Human Milk Lipase: Interaction with Proteins

Abstract

The initial rates of hydrolysis of triolein, catalyzed by bile-salt-stimulated hu man milk lipase, BSSL, were measured at pH 7.5 and 37 ° C, in the presence of selected proteins, namely immunoglobulin A, α-lactalbumin, lactoferrin, hen egg white lysozyme, pancreatic lipase, myoglobin and the very surface active protein melittin. The esterase activity of the enzyme against 4-nitro- phenylacetate was also measured in the presence of a number of different samples of lactoferrin. Under the conditions used, α-lactalbumin and hen egg white lysozyme had almost no effect on the lipase activity. Immunoglobulin A was slightly inhibitory; lactoferrin, pancreatic lipase and myoglobin were all partially inhibitory; and melittin was capable of almost completely inac tivating the lipase.