Effect of chemical modification of tyrosine residues on activities of bacterial lipase

Lipase from Pseudomonas sp. KWI-56 was subjected to chemical modification of amino acid residues. When His and Arg residues and carboxyl groups were modified, both lipase activity and esterase activity of the lipase were remarkably decreased. Modification of tyrosine residues of the lipase with tetranitromethane resulted in a decrease in the lipase activity to hydrolyze acylglycerides and their derivatives without an appreciable loss of the esterase activity to hydrolyze synthetic esters. It was found that the modification of at least one or two tyrosine residues among the 15 residues in a lipase molecule was enough to regulate the enzymatic functions described above.