InterPro domain: IPR007325

Kynurenine formamidase catalyses the hydrolysis of N-formyl-L-kynurenine to L-kynurenine, the second step in the kynurenine pathway of tryptophan degradation [ 1 ]. The proteins contain a conserved motif HXGTHXDXPXH that is likely to form a part of the active site.

This family also includes cyclase-like proteins from plants. They are involved in responses to abiotic stress, and could function as polyketide cyclases [ 2 ]. Isatin hydrolase ( 3.5.2.20 ), characterized from the bacterium Labrenzia aggregata, is also a member of this family. It is a manganese-binding enzyme that hydrolyses the cyclic amide bond (lactam) of isatin (1H-indole-2,3-dione) to yield isatinate (2-(2-aminophenyl)-2-oxoacetate), during the degradation of the plant hormone indole-3-acetic acid (IAA) [ 3 ].

1. Aerobic tryptophan degradation pathway in bacteria: novel kynurenine formamidase. FEMS Microbiol. Lett. 227, 219-27
2. Characterization of a novel cyclase-like gene family involved in controlling stress tolerance in rice. J. Plant Physiol. 181, 30-41
3. A proton wire and water channel revealed in the crystal structure of isatin hydrolase. J. Biol. Chem. 289, 21351-9