tailieunhanh - Báo cáo khoa học: Human kynurenine aminotransferase II – reactivity with substrates and inhibitors

Kynurenine aminotransferase (KAT) is a pyridoxal 5¢-phosphate-dependent enzyme that catalyzes the conversion of kynurenine, an intermediate of the tryptophan degradation pathway, into kynurenic acid, an endogenous antagonist of ionotropic excitatory amino acid receptors in the central ner-vous system. | 1FEBS Journal Human kynurenine aminotransferase II - reactivity with substrates and inhibitors Elisabetta Passera1 Barbara Campanini1 Franca Rossi2 Valentina Casazza2 Menico Rizzi2 Roberto Pellicciari3 and Andrea Mozzarelli1 4 1 Department of Biochemistry and Molecular Biology University of Parma Italy 2 DiSCAFF - Department of Chemical Food Pharmaceuticaland PharmacologicalSciences University of Piemonte Orientale A. Avogadro Novara Italy 3 Department of Drug Chemistry and Technology University of Perugia Italy 4 NationalInstitute of Biostructures and Biosystems Rome Italy Keywords kynurenine aminotransferase II KATII kynurenine pathway PLP-dependent enzymes schizophrenia tryptophan metabolism Correspondence A. Mozzarelli Department of Biochemistry and Molecular Biology University of Parma Viale GP Usberti 23 A 43100 Parma Italy Fax 39 0521 905151 Tel 39 0521 905138 E-mail Received 22 November 2010 revised 8 March 2011 accepted 22 March 2011 doi Kynurenine aminotransferase KAT is a pyridoxal 5 -phosphate-dependent enzyme that catalyzes the conversion of kynurenine an intermediate of the tryptophan degradation pathway into kynurenic acid an endogenous antagonist of ionotropic excitatory amino acid receptors in the central nervous system. KATII is the prevalent isoform in mammalian brain and a drug target for the treatment of schizophrenia. We have carried out a spectroscopic and functional characterization of both the human wild-type KATII and a variant carrying the active site mutation Tyr142 fi Phe. The transamination and the b-lytic activity of KATII towards the substrates kynurenine and a-aminoadipate the substrate analog b-chloroalanine and the inhibitors R -2-amino-4- 4- ethylsulfonyl -4-oxobutanoic acid and cysteine sulfinate were investigated with both conventional assays and a novel continuous spectrophotometric assay. Furthermore for high-throughput KATII inhibitor screenings an endpoint assay .