Abstract
An enzyme fraction in guinea pig liver catalyzing the hydrolysis of chloroacetyl α-naphthylamide was separated by gel filtration and demonstrated to hydrolyze N-formyl-l-kynurenine. On the basis of relative substrate hydrolysis rates, the enzymes in this peak were shown to have the characteristics of kynurenine formamidase, an enzyme catalyzing the transformation of N-formyl-l-kynurenine to l-kynurenine and formic acid. The histochemical localization in fixed tissue of the hydrolysis of chloroacetyl α-naphthylamide can be almost totally ascribed to this enzyme and, thereby, indicates tissue sites of tryptophan catabolism.