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Human glutaminase

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PDB Code 3CZD Target Class AA metabolic enzymes Target GLS Alias AAD20, DKFZp686O15119, FLJ10358, GLS, GLS1, KIAA0838 Disease Area/Function cancer Date Deposited Apr 29 2008 Authors T.KARLBERG, M.WELIN, J.ANDERSSON, C.H.ARROWSMITH, H.BERGLUND, R.D.BUSAM, R.COLLINS, L.G.DAHLGREN, A.M.EDWARDS, S.FLODIN, A.FLORES, S.GRASLUND, M.HAMMARSTROM, A.JOHANSSON, I.JOHANSSON, A.KALLAS, T.KOTENYOVA, L.LEHTIO, M.MOCHE, M.E.NILSSON, P.NORDLUND, T.NYMAN, C.PERSSON, J.SAGEMARK, L.SVENSSON, A.G.THORSELL, L.TRESAUGUES, S.VAN DEN BERG, M.WIKSTROM, H.SCHULER

About this structure

Glutaminase (GLS) catalyses the deamidation of glutamine to form glutamate and ammonia. In humans the enzyme is involved in several important aspects of energy and nitrogen metabolism, e.g. ammonia and urea metabolism in liver, and is also widely distributed in the brain. Glutamine is the molecule that couples ammonia metabolism to the synthesis of neurotransmitters glutamate and GABA. Excessive accumulation of glutamine in brain cells may be deleterious to brain function. The enzyme exists in two closely related isoforms GLS (kidney isoform) and GLS2 (liver isoform). GLS has been suggested to have implications in behavioral disorders due to the role of glutamate as a neurotransmitter.

Here the X-ray crystal structure of the human glutaminase GLS is presented in complex with the product L-glutamate at 2.4Å resolution. The structure was solved by molecular replacement using the structure of glutaminase from Micrococcus luteus K-3 (PDB entry 2DFW) as search model. Glutaminase forms a homodimer, and each monomer is a bifurcated fold with the active site between the two domains. Domain I is comprised of a five-stranded anti-parallel β–sheet surrounded by α–helices and loops (residues 222-281 and 424-531) while domain II is solely &alpha:–helical (residues 282-423). In the inter-domain cleft L-glutamate, added to the protein during crystallization, is clearly visible in the electron density and makes hydrogen bonds to Q285, S286, N335, E381, N388, Y414, Y466 and V484. Enzyme inhibition by L-glutamate has been reported but only for the kidney isoform of GLS. Interestingly the putative serine-lysine catalytic dyad (S286 and K289) is in close proximity to the bound glutamate, where S286 also makes interactions to the carboxyl moiety. The structure is an important advancement in understanding the biochemistry of the catalytic reaction.

References

  1. Albrecht, J. Sonnewald, U. Waagepetersen, HS. and Schousboe, A. (2007) Glutamine in the central nervous system: function and dysfunction. Front. Biosci. 12, 332-343.
  2. Campos-Sandoval, JA. López de la Oliva, AR. Lobo, C. Segura, JA. Matés, JM. Alonso, FJ. Márquez, J. (2007) Expression of functional human glutaminase in baculovirus system: Affinity purification, kinetic and molecular characterization. Int. J. Biochem. Cell Biol. 39, 765-773.
  3. Yoshimune, K. Shirakihara, Y. Shiratori, A. Wakayama, M. Chantawannakul, P. Moriguchi, M. (2006) Crystal structure of a major fragment of the salt-tolerant glutaminase from Micrococcus luteus K-3. Biochem. Biophys. Res. Commun. 346, 1118-1124.
  4. Curthoys, NP. and Watford, M., (1995). Regulation of glutaminase activity and glutamine metabolism. Annu. Rev. Nutr. 15, 133-159.