Hydrolyzes glucose-6-phosphate to glucose in the endoplasmic reticulum. May form with the glucose-6-phosphate transporter (SLC37A4/G6PT) a ubiquitously expressed complex responsible for glucose production through glycogenolysis and gluconeogenesis. Probably required for normal neutrophil function.
The liver endoplasmic reticulum glucose-6-phosphatase catalytic subunit (G6PC1) catalyses glucose 6-phosphate hydrolysis during gluconeogenesis and glycogenolysis. The highest glucose-6-phosphatase activities are found in the liver and the kidney; there have been many reports of glucose 6-phosphate hydrolysis in other tissues. We cloned a new G6Pase isoform (G6PC3) from human brain encoded by a six-exon gene (chromosome 17q21). G6PC3 protein was able to hydrolyse glucose 6-phosphate in transfected Chinese hamster ovary cells. The optimal pH for glucose 6-phosphate hydrolysis was lower and the K(m) higher relative to G6PC1. G6PC3 preferentially hydrolyzed other substrates including pNPP and 2-deoxy-glucose-6-phosphate compared to the liver enzyme.
J. Mol. Endocrinol. 29, 205-222 (2002)[PubMed:12370122]
Glucose-6-phosphatase (G6Pase) catalyzes the final step in the gluconeogenic and glycogenolytic pathways, the hydrolysis of glucose-6-phosphate (G6P) to glucose and phosphate. This paper describes the identification and characterization of a human cDNA and gene encoding a ubiquitously expressed G6Pase catalytic subunit-related protein (UGRP). The ORF of this UGRP cDNA encodes a protein (346 amino acids (aa); M(r) 38 709) which shares 36% overall identity to the human G6Pase catalytic subunit (357 aa; M(r) 40 487). UGRP exhibits a similar predicted transmembrane topology and conservation of many of the catalytically important residues with the G6Pase catalytic subunit; however, unlike the G6Pase catalytic subunit, UGRP does not catalyze G6P hydrolysis. UGRP mRNA was detected by RNA blot analysis in every tissue examined with the highest expression in muscle. Database analysis showed that the human UGRP gene is composed of six exons, spans approximately 5.4 kbp of genomic DNA and is located on chromosome 17q21 with the G6Pase catalytic subunit gene. The UGRP gene transcription start sites were mapped by primer extension analysis, and the activity of the UGRP gene promoter was analyzed using luciferase fusion gene constructs. In contrast to the G6Pase catalytic subunit gene promoter, the UGRP promoter was highly active in all cell lines examined.
A fine control of the blood glucose level is essential to avoid hyper- or hypo-glycemic shocks associated with many metabolic disorders, including diabetes mellitus and type I glycogen storage disease. Between meals, the primary source of blood glucose is gluconeogenesis and glycogenolysis. In the final step of both pathways, glucose-6-phosphate (G6P) is hydrolyzed to glucose by the glucose-6-phosphatase (G6Pase) complex. Because G6Pase (renamed G6Pase-alpha) is primarily expressed only in the liver, kidney, and intestine, it has implied that most other tissues cannot contribute to interprandial blood glucose homeostasis. We demonstrate that a novel, widely expressed G6Pase-related protein, PAP2.8/UGRP, renamed here G6Pase-beta, is an acid-labile, vanadate-sensitive, endoplasmic reticulum-associated phosphohydrolase, like G6Pase-alpha. Both enzymes have the same active site structure, exhibit a similar Km toward G6P, but the Vmax of G6Pase-alpha is approximately 6-fold greater than that of G6Pase-beta. Most importantly, G6Pase-beta couples with the G6P transporter to form an active G6Pase complex that can hydrolyze G6P to glucose. Our findings challenge the current dogma that only liver, kidney, and intestine can contribute to blood glucose homeostasis and explain why type Ia glycogen storage disease patients, lacking a functional liver/kidney/intestine G6Pase complex, are still capable of endogenous glucose production.
The chemical reactions and pathways involving glucose 6-phosphate, a monophosphorylated derivative of glucose with the phosphate group attached to C-6.
The directed movement of glucose-6-phosphate into, out of or within a cell, or between cells, by means of some agent such as a transporter or pore. Glucose-6-phosphate is a monophosphorylated derivative of glucose with the phosphate group attached to C-6.
IEAOrtholog Compara
Enzymatic activity
This protein acts as an enzyme. It is known to catalyze the following reaction
The liver endoplasmic reticulum glucose-6-phosphatase catalytic subunit (G6PC1) catalyses glucose 6-phosphate hydrolysis during gluconeogenesis and glycogenolysis. The highest glucose-6-phosphatase activities are found in the liver and the kidney; there have been many reports of glucose 6-phosphate hydrolysis in other tissues. We cloned a new G6Pase isoform (G6PC3) from human brain encoded by a six-exon gene (chromosome 17q21). G6PC3 protein was able to hydrolyse glucose 6-phosphate in transfected Chinese hamster ovary cells. The optimal pH for glucose 6-phosphate hydrolysis was lower and the K(m) higher relative to G6PC1. G6PC3 preferentially hydrolyzed other substrates including pNPP and 2-deoxy-glucose-6-phosphate compared to the liver enzyme.
A fine control of the blood glucose level is essential to avoid hyper- or hypo-glycemic shocks associated with many metabolic disorders, including diabetes mellitus and type I glycogen storage disease. Between meals, the primary source of blood glucose is gluconeogenesis and glycogenolysis. In the final step of both pathways, glucose-6-phosphate (G6P) is hydrolyzed to glucose by the glucose-6-phosphatase (G6Pase) complex. Because G6Pase (renamed G6Pase-alpha) is primarily expressed only in the liver, kidney, and intestine, it has implied that most other tissues cannot contribute to interprandial blood glucose homeostasis. We demonstrate that a novel, widely expressed G6Pase-related protein, PAP2.8/UGRP, renamed here G6Pase-beta, is an acid-labile, vanadate-sensitive, endoplasmic reticulum-associated phosphohydrolase, like G6Pase-alpha. Both enzymes have the same active site structure, exhibit a similar Km toward G6P, but the Vmax of G6Pase-alpha is approximately 6-fold greater than that of G6Pase-beta. Most importantly, G6Pase-beta couples with the G6P transporter to form an active G6Pase complex that can hydrolyze G6P to glucose. Our findings challenge the current dogma that only liver, kidney, and intestine can contribute to blood glucose homeostasis and explain why type Ia glycogen storage disease patients, lacking a functional liver/kidney/intestine G6Pase complex, are still capable of endogenous glucose production.
J. Mol. Endocrinol. 29, 205-222 (2002)[PubMed:12370122]
Glucose-6-phosphatase (G6Pase) catalyzes the final step in the gluconeogenic and glycogenolytic pathways, the hydrolysis of glucose-6-phosphate (G6P) to glucose and phosphate. This paper describes the identification and characterization of a human cDNA and gene encoding a ubiquitously expressed G6Pase catalytic subunit-related protein (UGRP). The ORF of this UGRP cDNA encodes a protein (346 amino acids (aa); M(r) 38 709) which shares 36% overall identity to the human G6Pase catalytic subunit (357 aa; M(r) 40 487). UGRP exhibits a similar predicted transmembrane topology and conservation of many of the catalytically important residues with the G6Pase catalytic subunit; however, unlike the G6Pase catalytic subunit, UGRP does not catalyze G6P hydrolysis. UGRP mRNA was detected by RNA blot analysis in every tissue examined with the highest expression in muscle. Database analysis showed that the human UGRP gene is composed of six exons, spans approximately 5.4 kbp of genomic DNA and is located on chromosome 17q21 with the G6Pase catalytic subunit gene. The UGRP gene transcription start sites were mapped by primer extension analysis, and the activity of the UGRP gene promoter was analyzed using luciferase fusion gene constructs. In contrast to the G6Pase catalytic subunit gene promoter, the UGRP promoter was highly active in all cell lines examined.
Protein involved in the biosynthesis of "new" glucose from such noncarbohydrate precursors as pyruvate, lactate, certain amino acids and intermediates of the tricarboxylic acid cycle.
Enzyme which catalyzes hydrolysis reaction, i.e. the addition of the hydrogen and hydroxyl ions of water to a molecule with its consequent splitting into two or more simpler molecules.
A reference proteome is a set of protein sequences derived from a complete proteome which constitutes a defined standard for a particular user community. Reference proteomes are manually defined according to a number of criteria. They cover the proteomes of well- studied model organisms and other proteomes of interest for biomedical and biotechnological research. Reference proteomes have been selected to provide broad coverage of the tree of life, and constitute a representative cross-section of the taxonomic diversity to be found within UniProtKB.
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