Catalase enzyme has two functions, first is catalytic and destroyed with high temperature. The second function oxidic , increasing with high temperature. The catalase enzyme effects on the substrate of ortho – phenylene diamine turning it into aromatic cancerogenus azo compounds organic acids such as, benzoic acid, salicylic acid and ascorbic acid inhibit the effect of catalase enzyme substrate ortho – phenylene diamine. The inhibition is competitive when the benzoic acid and salicylic acid effects , while the inhibition is non competitive when the ascorbic acid effect.