Esterase acyl binding site of human milk lipase.

The hydrolysis of a series of 4-nitrophenyl alkanoates and of 4-nitrophenylbenzoate and -methylbenzoate, catalysed by human milk lipase in the absence and presence of cholate stimulation, has been measured at pH 7.3, 37.5 degrees C. It has been shown that the enzyme possesses a specific esterase acyl binding site that is hydrophobic in nature and wide enough to accommodate one fatty acid chain, but not two. This binding site is unaffected by bile salt stimulation of the enzyme.