Bile salt-stimulated lipase in human milk and carboxyl ester hydrolase in pancreatic juice: Are they identical enzymes?

Abstract

Human milk contains a lipase that readily hydrolyzes a variety of ester substrates [l-3]. A distinguishing feature of this lipase is that for activity against emulsified long-chain triacylglycerols it requires primary bile salts [ 1,2]. This so-called bile salt-stimulatedlipase (BSSL)is an evolutionary newcomer as a milk enzyme; so far it has been found only in milk from man and gorilla (review [4]). Recent data strongly suggest that it has important roles, both quantitative and qualitative, for the digestion of milk lipids in the intestine of the breast-fed infant ([5], review [6]). Human pancreatic juice contains an enzyme which has been designated carboxyl ester hydrolase (CEH) [7]. This enzyme has many properties in common with BSSL, e.g., stimulation by bile salts, ability to hydrolyze retinyl esters, inhibition by organophosphates (cf. [4,6] and [7,8]). It is the only enzyme in human pancreatic juice with activity against cholesteryl esters [8]. BSSL crossreacts immunochemically with a protein in human pancreatic juice [9]. We have now compared immunochemical, molecular and kinetic properties of bile salt-stimulated lipase and carboxyl ester hydrolase. We conclude that the 2 enzymes are very similar but not identical.