The interaction between human pancreatic carboxylester hydrolase (bile-salt-stimulated lipase of human milk) and lactoferrin.

An interaction between lactoferrin and human pancreatic carboxylester hydrolase (carboxylic-ester hydrolase, EC 3.1.1.1) (of bile-salt-stimulated lipase from human milk) has been demonstrated using partition in an aqueous two-phase system. This binding was strongly increased by the presence of sodium taurocholate, giving an apparent dissociation constant of around 10(-7) M. With this constant, significant binding is expected to occur in the intestine of the newborn being breast-fed between lactoferrin and either the pancreatic carboxylester hydrolase or the milk bile-salt-stimulated lipase. For carboxylester hydrolase, the interaction with lactoferrin meant a 1.4-fold increase in hydrolytic activity against p-nitrophenylacetate and cholesterololeate. For the function of lactoferrin we have not studied the importance of this interaction.