[摘要]：Kynureninase has been described in bacteria, fungi and animals as an enzyme involved in the catabolic degradation pathway Of L-tryptophan. This pyridoxal 5'-phosphate (PLP)-dependent enzyme catalyzes the hydrolytic cleavage Of L-kynurenine and 3-hydroxy-L-kynurenine to yield L-alanine and either anthranilic or 3-hydroxyanthranilic acid, respectively. We identified a putative kynureninase gene from a Trypanosoma cruzi project aiming at the structural and functional characterization of more than 100 proteins differentially expressed during metacyclogenesis. This gene encodes a protein similar in size and sequence to kynureninases from other sources. This open reading frame was cloned and the recombinant enzyme was overexpressed. Recombinant T cruzi kynureninase was purified to homogeneity and its identity was confirmed by mass spectrometry. The apparent molecular mass of the native T cruzi kynureninase was estimated by gel filtration, suggesting that the protein is a homodimer. Circular dichroism spectrum indicated a mixture of alpha-helix and beta-sheet structure, expected for an aminotransferase fold. L-kynurenine, preferentially hydrolyzed by prokaryotic inducible kynureninases, and 3-hydroxy-L-kynurenine, the preferred substrate in fungi and vertebrates, are both catabolized equally well by T cruzi kynureninase. Further experimental assays will be performed to fully understand the importance of this enzyme for T cruzi metabolism. (C) 2009 Elsevier B.V. All rights reserved.
