l-Kynurenine is a metabolite of the amino acid l-tryptophan. Kynurenine formamidase (EC:3.5.1.9) catalyses the hydrolysis of N-formyl-L-kynurenine to L-kynurenine, the second step in the kynurenine pathway of tryptophan degradation. It is required for elimination of toxic metabolites