Inhibition of horseradish peroxidase by N-ethylamide of o-sulfobenzoylacetic acid

The carboxylic groups of horseradish peroxidase were modified by 1-cyclohex yl-3-(2-morpholinoethyl)carbo diimide metho-p-toluenesulfonate by the Koshl and method, The catalytic properties of the native and modified peroxidase were studied in the presence of N-ethylamide of o-sulfobenzoylacetic acid ( EASBA) at pH 5.0-7.5. In the oxidation of o-dianisicline,EASBA is a competi tive inhibitor of the carbidiimide-modified peroxidase and it increases bot h K-m and V-m in the case of the native enzyme, These data show that at lea st: one of the carboxylic groups modified with carbodiimide is located at t he area of the peroxidase active site.