Retention of enzymatic activity of bovine enterokinase after a limited reduction of disulfide bonds

Abstract

A limited reduction of disulfide bonds of bovine enterokinase has been accomplished by incubating the native enzyme with 5 mM dithioerythritol at 25°C for 2 hrs. After alkylation of the partially reduced protein with iodoacetate or iodoacetamide, the modified enzyme retained full enzymatic activity toward trypsinogen and thiobenzyl benzyloxycarbonyl L-lysinate. SDS-gel electrophoresis performed in the absence of mercaptoethanol showed that the heavy and light chains were no longer covalently bound to one another. Since the light chain retained full catalytic activity, intermolecular disulfide bonds holding the heavy and light chains together were non-essential for catalytic activity.