A Novel Variant of Glutamine

DeHaven, John E.; Robinson, Katherine A.; Nelson, Bryce A.; Buse, Maria G.

doi:10.2337/diabetes.50.11.2419

Cited by 47 publications

(31 citation statements)

References 29 publications

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“…GlcN-6-P accumulation would be predicted to have the greatest impact on kinetic measurements at the Fru 6-phosphate site. In this study, the K m measured for Fru-6-P was at least an order of magnitude lower than from previous reports, whereas the K m for L-Gln was similar to previous reports with mammalian GFAT (10,12,13,27,28). In our studies, the K m for Fru-6-P and the K i for GlcN-6-P were roughly equivalent.…”

Section: Discussioncontrasting

confidence: 52%

“…Huynh et al (10) reported the characterization of rat liver GFAT, and Milewski et al (8) reported the biochemical properties of the Candida enzyme, which exhibits similarities to the mammalian forms. Recent descriptions of the GFAT1 isoform, GFAT1Alt, demonstrated that GFAT1 and GFAT1Alt differ in their sensitivity to inhibition by UDP-GlcNAc (11,12). These studies agree that feedback regulation by the pathway end product, UDP-GlcNAc, is a common feature of all mammalian GFATs studied to date, unlike the bacterial forms (13,14).…”

supporting

confidence: 71%

“…The glutaminase assay coupled to glutamate dehydrogenase or the Morgan-Elson colorimetric assay requires at least 10 M product accumulation (13,27,28). The K m for Fru-6-P measured with overexpressed mouse GFAT1 and GFAT1Alt also differs significantly from that of hGFAT1 in this report (12). Although species or methodological differences might affect these measurements, it is also possible that the presence of phosphoglucoisomerase activity in cytosolic extracts can rapidly deplete Fru-6-P (30).…”

Section: Discussioncontrasting

confidence: 46%

“…The feedback inhibition of GFAT by the pathway end product, UDP-GlcNAc, was previously demonstrated as a key regulatory mechanism for limiting hexosamine biosynthesis by eukaryotic GFAT (12,13,27,28,38). Differences in the magnitude of measured K i for UDP-GlcNAc have not been resolved for mammalian GFATs.…”

Section: Discussionmentioning

confidence: 99%

“…The relative role of GFAT1 and GFAT2 in normal physiology and in disease states has yet to be elucidated. The discovery that the splice variant, GFAT1Alt, has a lower K i for UDP-GlcNAc than GFAT1 emphasizes the importance of understanding the expression and regulation of GFAT isoforms (12). Prior to the cloning and overexpression of the mammalian enzymes, biochemical studies of GFAT have been limited by the practical challenges of enzyme instability and assay sensitivity.…”

Section: Discussionmentioning

confidence: 99%

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Kinetic Characterization of Human Glutamine-fructose-6-phosphate Amidotransferase I

Broschat¹,

Gorka²,

Page³

et al. 2002

Journal of Biological Chemistry

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Glutamine-fructose-6-phosphate amidotransferase (GFAT) catalyzes the first committed step in the pathway for biosynthesis of hexosamines in mammals. A member of the N-terminal nucleophile class of amidotransferases, GFAT transfers the amino group from the L-glutamine amide to D-fructose 6-phosphate, producing glutamic acid and glucosamine 6-phosphate. The kinetic constants reported previously for mammalian GFAT implicate a relatively low affinity for the acceptor substrate, fructose 6-phosphate (Fru-6-P, K m 0.2-1 mM). Utilizing a new sensitive assay that measures the production of glucosamine 6-phosphate (GlcN-6-P), purified recombinant human GFAT1 (hGFAT1) exhibited a K m for Fru-6-P of 7 M, and was highly sensitive to product inhibition by GlcN-6-P. In a second assay method that measures the stimulation of glutaminase activity, a K d of 2 M was measured for Fru-6-P binding to hGFAT1. Further, we report that the product, GlcN-6-P, is a potent competitive inhibitor for the Fru-6-P site, with a K i measured of 6 M. Unlike other members of the amidotransferase family, where glutamate production is loosely coupled to amide transfer, we have demonstrated that hGFAT1 production of glutamate and GlcN-6-P are strictly coupled in the absence of inhibitors. Similar to other amidotransferases, competitive inhibitors that bind at the synthase site may inhibit the synthase activity without inhibiting the glutaminase activity at the hydrolase domain. GlcN-6-P, for example, inhibited the transfer reaction while fully activating the glutaminase activity at the hydrolase domain. Inhibition of hGFAT1 by the end product of the pathway, UDPGlcNAc, was competitive with a K i of 4 M. These data suggest that hGFAT1 is fully active at physiological levels of Fru-6-P and may be regulated by its product GlcN-6-P in addition to the pathway end product, UDP-GlcNAc.

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Section: Discussioncontrasting

confidence: 52%

supporting

confidence: 71%

Section: Discussioncontrasting

confidence: 46%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Kinetic Characterization of Human Glutamine-fructose-6-phosphate Amidotransferase I

Broschat¹,

Gorka²,

Page³

et al. 2002

Journal of Biological Chemistry

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Current Awareness

2002

Diabetes Metabolism Res

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In order to keep subscribers up‐to‐date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of diabetes/metabolism. Each bibliography is divided into 17 sections: 1 Books, Reviews & Symposia; 2 General; 3 Genetics; 4 Epidemiology; 5 Immunology; 6 Prediction; 7 Prevention; 8 Intervention: a) General; b) Pharmacology; 9 Pathology: a) General; b) Cardiovascular; c) Neurological; d) Renal; 10 Endocrinology & Metabolism; 11 Nutrition; 12 Animal Studies; 13 Techniques. Within each section, articles are listed in alphabetical order with respect to author (8 Weeks journals ‐ Search completed at 19th Dec 2001)

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Cellular glycosylation senses metabolic changes and modulates cell plasticity during epithelial to mesenchymal transition

Carvalho-Cruz

Alisson-Silva

Todeschini

et al. 2017

Developmental Dynamics

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Epithelial to mesenchymal transition (EMT) is a developmental program reactivated by tumor cells that leads to the switch from epithelial to mesenchymal phenotype. During EMT, cells are transcriptionally regulated to decrease E-cadherin expression while expressing mesenchymal markers such as vimentin, fibronectin, and N-cadherin. Growing body of evidences suggest that cells engaged in EMT undergo a metabolic reprograming process, redirecting glucose flux toward hexosamine biosynthesis pathway (HBP), which fuels aberrant glycosylation patterns that are extensively observed in cancer cells. HBP depends on nutrient availability to produce its end product UDP-GlcNAc, and for this reason is considered a metabolic sensor pathway. UDP-GlcNAc is the substrate used for the synthesis of major types of glycosylation, including O-GlcNAc and cell surface glycans. In general, the rate limiting enzyme of HBP, GFAT, is overexpressed in many cancer types that present EMT features as well as aberrant glycosylation. Moreover, altered levels of O-GlcNAcylation can modulate cell morphology and favor EMT. In this review, we summarize some of the current knowledge that correlates glucose metabolism, aberrant glycosylation and hyper O-GlcNAcylation supported by HBP that leads to EMT activation. Developmental Dynamics 247:481-491, 2018. © 2017 Wiley Periodicals, Inc.

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A Novel Variant of Glutamine

Cited by 47 publications

References 29 publications

Kinetic Characterization of Human Glutamine-fructose-6-phosphate Amidotransferase I

Kinetic Characterization of Human Glutamine-fructose-6-phosphate Amidotransferase I

Current Awareness

Cellular glycosylation senses metabolic changes and modulates cell plasticity during epithelial to mesenchymal transition

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