2hzp
From Proteopedia
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Crystal Structure of Homo Sapiens Kynureninase
Overview
Kynureninase is a member of a large family of catalytically diverse but, structurally homologous pyridoxal 5'-phosphate (PLP) dependent enzymes, known as the aspartate aminotransferase superfamily or alpha-family. The, Homo sapiens and other eukaryotic constitutive kynureninases, preferentially catalyze the hydrolytic cleavage of 3-hydroxy-l-kynurenine, to produce 3-hydroxyanthranilate and l-alanine, while l-kynurenine is the, substrate of many prokaryotic inducible kynureninases. The human enzyme, was cloned with an N-terminal hexahistidine tag, expressed, and purified, from a bacterial expression system using Ni metal ion affinity, chromatography. Kinetic characterization of the recombinant enzyme reveals, classic Michaelis-Menten behavior, with a Km of 28.3 +/- 1.9 muM and a, specific activity of 1.75 mumol min-1 mg-1 for 3-hydroxy-dl-kynurenine., Crystals of recombinant kynureninase that diffracted to 2.0 A were, obtained, and the atomic structure of the PLP-bound holoenzyme was, determined by molecular replacement using the Pseudomonas fluorescens, kynureninase structure (PDB entry 1qz9) as the phasing model. A structural, superposition with the P. fluorescens kynureninase revealed that these two, structures resemble the "open" and "closed" conformations of aspartate, aminotransferase. The comparison illustrates the dynamic nature of these, proteins' small domains and reveals a role for Arg-434 similar to its role, in other AAT alpha-family members. Docking of 3-hydroxy-l-kynurenine into, the human kynureninase active site suggests that Asn-333 and His-102 are, involved in substrate binding and molecular discrimination between, inducible and constitutive kynureninase substrates.
About this Structure
2HZP is a Single protein structure of sequence from Homo sapiens with PLP as ligand. Active as Kynureninase, with EC number 3.7.1.3 Full crystallographic information is available from OCA.
Reference
Crystal Structure of Homo sapiens Kynureninase(,)., Lima S, Khristoforov R, Momany C, Phillips RS, Biochemistry. 2007 Mar 13;46(10):2735-44. Epub 2007 Feb 15. PMID:17300176
Page seeded by OCA on Mon Nov 12 22:39:03 2007
