Biochemical and Structural Properties of Mouse Kynurenine Aminotransferase III

Journal Article · Thu Jan 01 04:00:00 EST 2009 · Molecular and Cellular Biology

DOI:https://doi.org/10.1128/MCB.01272-08· OSTI ID:980038

Han, Q; Robinson, H; Cai, T; Tagle, D; Li, J

Kynurenine aminotransferase III (KAT III) has been considered to be involved in the production of mammalian brain kynurenic acid (KYNA), which plays an important role in protecting neurons from overstimulation by excitatory neurotransmitters. The enzyme was identified based on its high sequence identity with mammalian KAT I, but its activity toward kynurenine and its structural characteristics have not been established. In this study, the biochemical and structural properties of mouse KAT III (mKAT III) were determined. Specifically, mKAT III cDNA was amplified from a mouse brain cDNA library, and its recombinant protein was expressed in an insect cell protein expression system. We established that mKAT III is able to efficiently catalyze the transamination of kynurenine to KYNA and has optimum activity at relatively basic conditions of around pH 9.0 and at relatively high temperatures of 50 to 60C. In addition, mKAT III is active toward a number of other amino acids. Its activity toward kynurenine is significantly decreased in the presence of methionine, histidine, glutamine, leucine, cysteine, and 3-hydroxykynurenine. Through macromolecular crystallography, we determined the mKAT III crystal structure and its structures in complex with kynurenine and glutamine. Structural analysis revealed the overall architecture of mKAT III and its cofactor binding site and active center residues. This is the first report concerning the biochemical characteristics and crystal structures of KAT III enzymes and provides a basis toward understanding the overall physiological role of mammalian KAT III in vivo and insight into regulating the levels of endogenous KYNA through modulation of the enzyme in the mouse brain.

• Research Organization: Brookhaven National Laboratory (BNL) National Synchrotron Light Source
• Sponsoring Organization: Doe - Office Of Science
• DOE Contract Number: AC02-98CH10886
• OSTI ID: 980038
• Report Number(s): BNL--92956-2010-JA
• Journal Information: Molecular and Cellular Biology, Journal Name: Molecular and Cellular Biology Journal Issue: 3 Vol. 29; ISSN 0270-7306; ISSN MCEBD4
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
59 BASIC BIOLOGICAL SCIENCES
99 GENERAL AND MISCELLANEOUS
AMINO ACIDS
AMINOTRANSFERASES
ARCHITECTURE
BRAIN
CRYSTAL STRUCTURE
CRYSTALLOGRAPHY
CYSTEINE
ENZYMES
GLUTAMINE
HETEROCYCLIC ACIDS
HISTIDINE
HYDROXY COMPOUNDS
IN VIVO
INSECTS
KYNURENINE
LEUCINE
LEVELS
METHIONINE
MODULATION
NERVE CELLS
PRODUCTION
PROTEINS
QUINOLINES
RESIDUES
TEMPERATURE RANGE 0400-1000 K
national synchrotron light source