Kinetic properties of human milk bile salt-activated lipase: studies using long chain triacylglycerol as substrate.
Studies on the hydrodynamic properties of human milk bile salt-activated lipase (BAL) indicated that it is a monomer with molecular weight of 107,000. The presence of taurocholate (1 mM) did not lead to an association of the enzyme. The enzyme had a basal activity with trioctanoylglycerol and with shorter chain, but not with longer chain, monoacid triacylglycerols. Based on kinetic analyses, we suggest that the BAL-catalyzed lipolysis of long-chain triacylglycerol can be described to follow a compulsory sequential mechanism. The initial interaction of BAL with the activator (taurocholate) leads to a conformational change of the enzyme which facilitates the further interaction with the long chain triacylglycerol substrate in forming the enzyme-bile salt-substrate ternary complex. We also suggest that the binding of BAL with substrate involves direct interaction of the active site with the fatty acyl-chain of the triacylglycerol rather than with nonspecific hydrophobic interactions at the emulsion interface.
D001647:Bile Acids and Salts / Q000378:metabolism; D004655:Emulsions; D004789:Enzyme Activation; D005260:Female; D006801:Humans; D007700:Kinetics; D008049:Lipase / Q000378:metabolism*; D008895:Milk, Human / Q000201:enzymology*; D008970:Molecular Weight; D011485:Protein Binding; D013656:Taurocholic Acid / Q000378:metabolism; D014280:Triglycerides / Q000378:metabolism*
D001647:Bile Acids and Salts; D004655:Emulsions; D014280:Triglycerides; D013656:Taurocholic Acid; D008049:Lipase