Catalytic properties of modified human pancreatic carboxylic-ester hydrolase.

Human pancreatic carboxylic-ester hydrolase (EC 3.1.1.1) modified by specific reagents (diisopropyl phosphorofluoridate, diethyl p-nitrophenyl phosphate, Woodward's K reagent and ethoxyformic anhydride) was studied for its activity. The three residues probably implicated in the active site acting on soluble substrate are shown to be essential for the activity on emulsified substrates such as tributyrin or cholesterol esters solubilized by bile salts (hydrolyzing and synthetizing activities). The modified enzyme is still able to bind to interfaces. Nevertheless, one supplementary carboxylic acid group is responsible for the stability of the enzyme bound to interfaces.