| Structural highlights
Function
[GLSK_MOUSE] Catalyzes the first reaction in the primary pathway for the renal catabolism of glutamine. Plays a role in maintaining acid-base homeostasis. Regulates the levels of the neurotransmitter glutamate in the brain.[1] [2] [3]
Publication Abstract from PubMed
Glutamine-derived carbon becomes available for anabolic biosynthesis in cancer cells via the hydrolysis of glutamine to glutamate, as catalyzed by GAC, a splice variant of kidney-type glutaminase (GLS). Thus, there is significant interest in understanding the regulation of GAC activity, with the suggestion being that higher order oligomerization is required for its activation. We used x-ray crystallography, together with site-directed mutagenesis, to determine the minimal enzymatic unit capable of robust catalytic activity. Mutagenesis of the helical interface between the two pairs of dimers comprising a GAC tetramer yielded a non-active, GAC dimer whose x-ray structure displays a stationary loop ("activation loop") essential for coupling the binding of allosteric activators like inorganic phosphate to catalytic activity. Further mutagenesis that removed constraints on the activation loop yielded a constitutively active dimer, providing clues regarding how the activation loop communicates with the active site, as well as with a peptide segment that serves as a "lid" to close off the active site following substrate binding. Our studies show that the formation of large GAC oligomers is not a pre-requisite for full enzymatic activity. They also offer a mechanism by which the binding of activators like inorganic phosphate enables the activation loop to communicate with the active site to ensure maximal rates of catalysis, and promotes the opening of the lid to achieve optimal product release. Moreover, these findings provide new insights into how other regulatory events might induce GAC activation within cancer cells.
Mechanistic Basis of Glutaminase Activation: A KEY ENZYME THAT PROMOTES GLUTAMINE METABOLISM IN CANCER CELLS.,Li Y, Erickson JW, Stalnecker CA, Katt WP, Huang Q, Cerione RA, Ramachandran S J Biol Chem. 2016 Sep 30;291(40):20900-20910. doi: 10.1074/jbc.M116.720268. Epub , 2016 Aug 19. PMID:27542409[4]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Masson J, Darmon M, Conjard A, Chuhma N, Ropert N, Thoby-Brisson M, Foutz AS, Parrot S, Miller GM, Jorisch R, Polan J, Hamon M, Hen R, Rayport S. Mice lacking brain/kidney phosphate-activated glutaminase have impaired glutamatergic synaptic transmission, altered breathing, disorganized goal-directed behavior and die shortly after birth. J Neurosci. 2006 Apr 26;26(17):4660-71. PMID:16641247 doi:10.1523/JNEUROSCI.4241-05.2006
- ↑ El Hage M, Masson J, Conjard-Duplany A, Ferrier B, Baverel G, Martin G. Brain slices from glutaminase-deficient mice metabolize less glutamine: a cellular metabolomic study with carbon 13 NMR. J Cereb Blood Flow Metab. 2012 May;32(5):816-24. doi: 10.1038/jcbfm.2012.22. Epub, 2012 Feb 29. PMID:22373647 doi:10.1038/jcbfm.2012.22
- ↑ Cassago A, Ferreira AP, Ferreira IM, Fornezari C, Gomes ER, Greene KS, Pereira HM, Garratt RC, Dias SM, Ambrosio AL. Mitochondrial localization and structure-based phosphate activation mechanism of Glutaminase C with implications for cancer metabolism. Proc Natl Acad Sci U S A. 2012 Jan 24;109(4):1092-7. Epub 2012 Jan 6. PMID:22228304 doi:10.1073/pnas.1112495109
- ↑ Li Y, Erickson JW, Stalnecker CA, Katt WP, Huang Q, Cerione RA, Ramachandran S. Mechanistic Basis of Glutaminase Activation: A KEY ENZYME THAT PROMOTES GLUTAMINE METABOLISM IN CANCER CELLS. J Biol Chem. 2016 Sep 30;291(40):20900-20910. doi: 10.1074/jbc.M116.720268. Epub , 2016 Aug 19. PMID:27542409 doi:http://dx.doi.org/10.1074/jbc.M116.720268
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