Human Hexose-6-phosphate Dehydrogenase (Glucose 1-Dehydrogenase) Encoded at 1p36: Coding Sequence and Expression

doi:10.1006/bcmd.1999.0224

Blood Cells, Molecules, and Diseases

Volume 25, Issue 1, February 1999, Pages 30-37

https://doi.org/10.1006/bcmd.1999.0224 Get rights and content

Abstract

ABSTRACT: Using the published protein sequence from a rabbit microsomal glucose-6-phosphate dehydrogenase G6PD we have isolated and sequenced a cDNA clone coding for its human equivalent, which is also known as hexose-6-phosphate dehydrogenase (H6PD) and glucose dehydrogenase. The corresponding genomic sequence is in the databases enabling its localization to chromosome 1p36. The gene spans 37 kb and consists of 5 exons, the fifth of which codes for more than half of the 89kDa protein. The first intron is a 10kb insertion in the 5′ untranslated sequence. The predicted mRNA has an exceptionally long (6.5kb) 3′ untranslated sequence. The predicted protein shows extensive homology with X-linked G6PD, suggesting the two genes share a common ancestor but no intron positions are conserved between the two genes suggesting the gene duplication was an ancient event. The C-terminal portion of the protein is not homologous with G6PD but shows limited homology with proteins of unknown function found throughout evolution and encoded next to G6PD in various micro-organisms. Intriguingly this C-terminal portion has some homology with the N-terminal sequence ofPlasmodium falciparumG6PD.

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Cited by (46)

High-resolution structural-omics of human liver enzymes
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We applied raw human liver microsome lysate to a holey carbon grid and used cryo-electron microscopy (cryo-EM) to define its composition. From this sample we identified and simultaneously determined high-resolution structural information for ten unique human liver enzymes involved in diverse cellular processes. Notably, we determined the structure of the endoplasmic bifunctional protein H6PD, where the N- and C-terminal domains independently possess glucose-6-phosphate dehydrogenase and 6-phosphogluconolactonase enzymatic activity, respectively. We also obtained the structure of heterodimeric human GANAB, an ER glycoprotein quality-control machinery that contains a catalytic α subunit and a noncatalytic β subunit. In addition, we observed a decameric peroxidase, PRDX4, which directly contacts a disulfide isomerase-related protein, ERp46. Structural data suggest that several glycosylations, bound endogenous compounds, and ions associate with these human liver enzymes. These results highlight the importance of cryo-EM in facilitating the elucidation of human organ proteomics at the atomic level.
11β-Hydroxysteroid dehydrogenase 1: Regeneration of active glucocorticoids is only part of the story
2015, Journal of Steroid Biochemistry and Molecular Biology
Citation Excerpt :
H6PDH catalyzes the first two steps of the pentose phosphate pathway in the ER and represents a major source of intraluminal NADPH. In contrast to the cytosolic glucose-6-phosphate dehydrogenase, H6PDH has a broader substrate specifity, not discriminating between glucose-6-phosphate, galactose-6-phosphate, 2-deoxyglucose-6-phosphate and other hexose-6-derivatives [16–19]. Nevertheless, it is believed that under physiological conditions, H6PDH utilizes glucose-6-phosphate as its main substrate [18].
11β-Hydroxysteroid dehydrogenase 1 (11β-HSD1) is an endoplasmic reticulum membrane enzyme with its catalytic site facing the luminal space. It functions primarily as a reductase, driven by the supply of its cosubstrate NADPH by hexose-6-phosphate dehydrogenase (H6PDH). Extensive research has been performed on the role of 11β-HSD1 in the regeneration of active glucocorticoids and its role in inflammation and metabolic disease. Besides its important role in the fine-tuning of glucocorticoid action, 11β-HSD1 is a multi-functional carbonyl reductase converting several 11- and 7-oxosterols into the respective 7-hydroxylated forms. Moreover, 11β-HSD1 has a role in phase I biotransformation reactions and catalyzes the carbonyl reduction of several non-steroidal xenobiotics. Recent observations from experiments using selective inhibitors and studies with transgenic mice indicated a role for 11β-HSD1 in oxysterol metabolism and in bile acid homeostasis, with evidence for glucocorticoid-independent effects on gene expression. This review focuses on the promiscuity of 11β-HSD1 to accept structurally distinct substrates and discusses recent progress mainly on non-glucocorticoid substrates.
This article is part of a Special Issue entitled ‘Enzyme Promiscuity and Diversity’.
Biochemistry and physiology of hexose-6-phosphate knockout mice
2011, Molecular and Cellular Endocrinology
Citation Excerpt :
H6PDH is a bifunctional enzyme which is able to catalyze the first two reactions of an endoplasmic reticulum (ER) specific pentose phosphate pathway (Bublitz and Steavenson, 1988). H6PDH protein was initially purified from rabbit liver microsomes (Ozols, 1993) and this allowed the cloning and identification of the human H6PDH cDNA and gene (Mason et al., 1999). Sequence homology analyses indicate that H6PDH is biochemically distinct from the glucose-6-phosphate dehydrogenase (G6PDH) which catalyzes the same reaction in the cytosol, although the extensive homology between these two genes suggests they share a common ancestor (Clarke and Mason, 2003; Hewitt et al., 2005; Mason et al., 1999).
Hexose-6-phosphate dehydrogenase (H6PDH) has emerged as an important factor in setting the redox status of the endoplasmic reticulum (ER) lumen. An important role of H6PDH is to generate a high NADPH/NADP⁺ ratio which permits 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) to act as an oxo-reductase, catalyzing the activation of glucocorticoids (GCs). In H6PDH knockout mice 11β-HSD1 assumes dehydrogenase activity and inactivates GCs, rendering the target cell relatively GC insensitive. Consequently, H6PDHKO mice have a phenotype consistent with defects in the permissive and adaptive actions of GCs upon physiology. H6PDHKO mice have also offered an insight into muscle physiology as they also present with a severe vacuolating myopathy, abnormalities of glucose homeostasis and activation of the unfolded protein response due to ER stress, and a number of mechanisms driving this phenotype are thought to be involved. This article will review what we understand of the redox control of GC hormone metabolism regulated by H6PDH, and how H6PDHKO mice have allowed an in-depth understanding of its potentially novel, GC-independent roles in muscle physiology.
The glucocorticoid-activating enzyme 11β-hydroxysteroid dehydrogenase type 1 has broad substrate specificity: Physiological and toxicological considerations
2010, Journal of Steroid Biochemistry and Molecular Biology
The primary function of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) is to catalyze the conversion of inactive to active glucocorticoid hormones and to modulate local glucocorticoid-dependent gene expression. Thereby 11β-HSD1 plays a key role in the regulation of metabolic functions and in the adaptation of the organism to energy requiring situations. Importantly, elevated 11β-HSD1 activity has been associated with metabolic disorders, and recent investigations with rodent models of obesity and type 2 diabetes provided evidence for beneficial effects of 11β-HSD1 inhibitors, making this enzyme a promising therapeutic target. Several earlier and recent studies, mainly performed in vitro, revealed a relatively broad substrate spectrum of 11β-HSD1 and suggested that this enzyme has additional functions in the metabolism of some neurosteroids (7-oxy- and 11-oxyandrogens and -progestins) and 7-oxysterols, as well as in the detoxification of various xenobiotics that contain reactive carbonyl groups. While there are many studies on the effect of inhibitors on cortisone reduction and circulating glucocorticoid levels and on the transcriptional regulation of 11β-HSD1 in obesity and diabetes, only few address the so-called alternative functions of this enzyme. We review recent progress on the biochemical characterization of 11β-HSD1, with a focus on cofactor and substrate specificity and on possible alternative functions of this enzyme.
Direct protein-protein interaction of 11β-hydroxysteroid dehydrogenase type 1 and hexose-6-phosphate dehydrogenase in the endoplasmic reticulum lumen
2008, Biochimica et Biophysica Acta - Molecular Cell Research
Hexose-6-phosphate dehydrogenase (H6PDH) has been shown to stimulate 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1)-dependent local regeneration of active glucocorticoids. Here, we show that coexpression with H6PDH results in a dramatic shift from 11β-HSD1 oxidase to reductase activity without affecting the activity of the endoplasmic reticular enzyme 17β-HSD2. Immunoprecipitation experiments revealed coprecipitation of H6PDH with 11β-HSD1 but not with the related enzymes 11β-HSD2 and 17β-HSD2, suggesting a specific interaction between H6PDH and 11β-HSD1. The use of the 11β-HSD1/11β-HSD2 chimera indicates that the N-terminal 39 residues of 11β-HSD1 are sufficient for interaction with H6PDH. An important role of the N-terminus was indicated further by the significantly stronger interaction of 11β-HSD1 mutant Y18-21A with H6PDH compared to wild-type 11β-HSD1. The protein–protein interaction and the involvement of the N-terminus of 11β-HSD1 were confirmed by Far-Western blotting. Finally, fluorescence resonance energy transfer (FRET) measurements of HEK-293 cells expressing fluorescently labeled proteins provided evidence for an interaction between 11β-HSD1 and H6PDH in intact cells. Thus, using three different methods, we provide strong evidence that the functional coupling between 11β-HSD1 and H6PDH involves a direct physical interaction of the two proteins.
Deletion of hexose-6-phosphate dehydrogenase activates the unfolded protein response pathway and induces skeletal myopathy
2008, Journal of Biological Chemistry
Hexose-6-phosphate dehydrogenase (H6PD) is the initial component of a pentose phosphate pathway inside the endoplasmic reticulum (ER) that generates NADPH for ER enzymes. In liver H6PD is required for the 11-oxoreductase activity of 11β-hydroxysteroid dehydrogenase type 1, which converts inactive 11-oxo-glucocorticoids to their active 11-hydroxyl counterparts; consequently, H6PD null mice are relatively insensitive to glucocorticoids, exhibiting fasting hypoglycemia, increased insulin sensitivity despite elevated circulating levels of corticosterone, and increased basal and insulin-stimulated glucose uptake in muscles normally enriched in type II (fast) fibers, which have increased glycogen content. Here, we show that H6PD null mice develop a severe skeletal myopathy characterized by switching of type II to type I (slow) fibers. Running wheel activity and electrically stimulated force generation in isolated skeletal muscle are both markedly reduced. Affected muscles have normal sarcomeric structure at the electron microscopy level but contain large intrafibrillar membranous vacuoles and abnormal triads indicative of defects in structure and function of the sarcoplasmic reticulum (SR). SR proteins involved in calcium metabolism, including the sarcoplasmic/endoplasmic reticulum calcium ATPase (SERCA), calreticulin, and calsequestrin, show dysregulated expression. Microarray analysis and real-time PCR demonstrate overexpression of genes encoding proteins in the unfolded protein response pathway. We propose that the absence of H6PD induces a progressive myopathy by altering the SR redox state, thereby impairing protein folding and activating the unfolded protein response pathway. These studies thus define a novel metabolic pathway that links ER stress to skeletal muscle integrity and function.

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^☆: communicated by Ernest, Beutler, M.D.01/18/99

^f1: Reprint request to: Dr. Philip J. Mason, Department of Haematology, Royal Postgraduate Medical School, Hammersmith Hospital, Ducane Road, London W12 ONN, UK, phone 0181-383-3235, fax 0181-742-9335, [email protected].

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Regular ArticleHuman Hexose-6-phosphate Dehydrogenase (Glucose 1-Dehydrogenase) Encoded at 1p36: Coding Sequence and Expression☆

Abstract

Regular Article
Human Hexose-6-phosphate Dehydrogenase (Glucose 1-Dehydrogenase) Encoded at 1p36: Coding Sequence and Expression☆