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Query: EC:1.1.1.49 (glucose-6-phosphate dehydrogenase)
7,794 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. A soluble enzyme which catalyses the NADPH-dependent reduction of 4-nitroacetophenone to 4-nitrophenylmethylcarbinol has been partially purified from human erythrocytes. 2.inter-individual or intra-individual differences in the enzymic activity were small except for very low activity observed in one subject with glucose 6-phosphate dehydrogenase deficiency resulting in decreased levels of NADPH. 3. The enzyme was inactivated above 50 degrees or on storage at 4 degrees for longer than 24 h. The pH optimum was between 7-0-8-0. 4. the enzyme has been differentiated from NADPH-methaemoglobin reductase, NADPH-cytochrome c reductase, glutathione reductase, alpha,beta-unsaturated ketone reductase and aromatic alpha-keto acid reductase activities, but similarities exist between this enzyme and a rabbit kidney cortex aromatic aldehyde/ketone reductase.
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PMID:The partial purification and properties of a human erythrocyte 4-nitroacetophenone reductase. 23 88

The activity of glucose-6-phosphate dehydrogenase (EC 1.1.1.49) FROM SPINACH CHLOROPLASTS IS STRONGLY REGULATED BY THE RATIO OF NADPH/NADP+, with the extent of this regulation controlled by the concentration of ribulose 1,5-diphosphate. Other metabolites of the reductive pentose phosphate cycle are far less effective in mediating the regulation of the enzyme activity by NADPH/NADP+ ratio. With a ratio of NADPH/NADP+ of 2, and a concentration of ribulose 1,5-diphosphate of 0.6 mM, the activity of the enzyme is completely inhibited. This level of ribulose 1,5-diphosphate is well within the concentration range which has been reported for unicellular green algae photosynthesizing in vivo. Ratios of NADPH/NADP+ of 2.0 have been measured for isolated spinach chloroplasts in the light and under physiological conditions. Since ribulose 1,5-diphosphate is a metabolite unique to the reductive pentose phosphate cycle and inhibits glucose-6-phosphate dehydrogenase in the presence of NADPH/NADP+ ratios found in chloroplasts in the light, it is proposed that regulation of the oxidative pentose phosphate cycle is accomplished in vivo by the levels of ribulose 1,5-diphosphate, NADPH, and NADP+. It already has been shown that several key reactions of the reductive pentose phosphate cycle in chloroplasts are regulated by levels of NADPH/NADP+ or other electron-carrying cofactors, and at least one key-regulated step, the carboxylation reaction is strongly affected by 6-phosphogluconate, the metabolic unique to the oxidative pentose phosphate cycle. Thus there is an interesting inverse regulation system in chloroplasts, in which reduced/oxidized coenzymes provide a general regulatory mechanism. The reductive cycle is activated at high NADPH/NADP+ ratios where the oxidative cycle is inhibited, and ribulose 1,5-diphosphate and 6-phosphogluconate provide further control of the cycles, each regulating the cycle in which it is not a metabolite.
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PMID:Regulation of glucose-6-phosphate dehydrogenase in spinach chloroplasts by ribulose 1,5-diphosphate and NADPH/NADP+ ratios. 23 45

A number of derivatives of NADP(H) were tested with respect to their effectiveness in interacting with tetrameric glucose 6-phosphate dehydrogenase (G6PD) retaining only the fraction of "structural" coenzyme (4 moles NADP). Interaction was probed by two parameters: a) increased thermostability of G6PD activity, measured as the difference in the corresponding transition temperature (Tm) of samples containing and lacking the NADP derivatives, respectively; b) competitive inhibition toward NADP, expressed a Ki values. Protection afforded by the various effectors against thermal denaturation decreased in the following order: NADPH, NADP, PADP-ribose, adenosine 2',5'-P2. Other NADP derivatives, including 2',3' cyclic NADP, NMN, NMNH, nicotinamide, adenosine 2'-P, were uneffective in respect to this property. The kinetically measured affinity was the greatest for NADPH and decreased progressively for the following effectors: PADP-ribose, NADP, NMNH, PADP-glycolaldehyde, adenosine 2',5'-P2, PADP-ribitol, adenosine 2'-P. Nicotinamide and NMN were uneffective on NADP binding. These data show that the adenosine moiety of NADP is more critically involved than the nicotinamide portion in the interaction with human G6PD.
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PMID:Human erythrocyte glucose 6-phosphate dehydrogenase. Influence of coenzyme derivatives on thermostability and kinetic properties. 23 15

Glucose dehydrogenase from rat liver microsomes was found to react not only with glucose as a substrate but also with glucose 6-phosphate, 2-deoxyglucose 6-phosphate and galactose 6-phosphate. The relative maximum activity of this enzyme was 29% for glucose 6-phosphate, 99% for 2-deoxyglucose 6-phosphate, and 25% for galactose 6-phosphate, compared with 100% for glucose with NADP. The enzyme could utilize either NAD or NADP as a coenzyme. Using polyacrylamide gradient gel electrophoresis, we were able to detect several enzymatically active bands by incubation of the gels in a tetrazolium assay mixture. Each band had different Km values for the substrates (3.0 x 10(-5)M glucose 6-phosphate with NADP to 2.4M glucose with NAD) and for coenzymes (1.3 x 10(-6)M NAD with galactose 6-phosphate to 5.9 x 10(-5)M NAD with glucose). Though glucose 6-phosphate and galactose 6-phosphate reacted with glucose dehydrogenase, they inhibited the reaction of this enzyme only when either glucose or 2-deoxyglucose 6-phosphate was used as a substrate. The Ki values for glucose 6-phosphate with glucose as substrate were 4.0 x 10(-6)M with NAD, and 8.4 x 10(-6)M with NADP; for galactose 6-phosphate they were 6.7 x10(-6)M with NAD and 6.0 x 10(-6)M with NADP. The Ki values for glucose 6-phosphate with 2-deoxyglucose 6-phosphate as substrate were 6.3 x 10(-6)M with NAD and 8.9 x 10(-6)M with NADP; and for galactose 6-phosphate, 8.0 x 10(-6)M with NAD and 3.5 x 10(-6)M with NADP. Both NADH and NADPH inhibited glucose dehydrogenase when the corresponding oxidized coenzymes were used (Ki values: 8.0 x 10(-5)M by NADH and 9.1 x 10(-5)M by NADPH), while only NADPH inhibited cytoplasmic glucose 6-phosphate dehydrogenase (Ki: 2.4 x 10(-5)M). The results indicate that glucose dehydrogenase cannot directly oxidize glucose in vivo, but it might play a similar role to glucose 6-phosphate dehydrogenase. The differences in the kinetics of glucose dehydrogenase and glucose 6-phosphate dehydrogenase show that glucose 6-phosphate and galactose 6-phosphate could be metabolized in quite different ways in the microsomes and cytoplasm of rat liver.
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PMID:Kinetic studies on microsomal glucose dehydrogenase in rat liver. 24 Jul 70

The effect of pre- and postnatal undernutrition on the neuronal enzymatic maturation of the neocerebellar hemispheral lobules VI b, VI c and VII (according to Larsell 1952) was studied. Postnatally oxidative enzyme histochemistry (LDH, SDH, NADH, NADPH, G6PDH) revealed a delayed enzymatic development in the cerebellum between days 8 and 22, as an effect of pre- and postnatal undernutrition. In the Purkinje cell apical cone a delayed increase in enzyme activities could be seen at days 8 to 11 as well as a delayed decrease in Purkinje cell perikaryal enzyme activities at days 11 to 14 post-partum. The retarded enzymatic development seemed to parallel the retarded morphological development (cf. Sima & Persson 1975).
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PMID:The effect of pre- and postnatal undernutrition on the development of the cerebellar cortex in the rat. II. Histochemical observations. 24 Oct 29

A study of the ultrastructural localization of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD), 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD), glucose-6-phosphate dehydrogenase (G-6-PD), beta-hydroxybutyrate dehydrogenase (beta-HBD), NADH diaphorase (NADH-D) and NADPH diaphorase (NADPH-D) in the guinea-pig testis is reported. The procedures employed included short immersion or perfusion fixation with aldehydes followed by incubation of small blocks in a tetrazolium salt or a ferricyanide medium. The effects of incubation conditions were investigated, and a reaction medium for the ultracytochemical demonstration of 11 beta-HSD is described. Using suitable controls, evidence for the specificity of the cytochemical reactions is presented. It was found that all the enzymes studied were present in both the Leydig and Sertoli cells of the guinea-pig testis and that the intracellular distribution pattern for each enzyme was independent of the cell type. Using tetrazolium salt techniques, both 3 beta-HSD and 11 beta-HSD activities were localized on or in membranes of smooth endoplasmic reticulum and within the mitochondria. With the ferricyanide techniques, G-6-PD activity was found to be associated mainly with the smooth endoplasmic reticulum membranes, while beta-HBD activity was limited to mitochondria. With both the tetrazolium salt and ferricyanide techniques, the reaction products for NADH-D and NADPH-D activities showed localizations which were similar to those observed for the steroid dehydrogenases.
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PMID:The ultrastructural localization of the enzymes related to steroid hormone metabolism in the guinea-pig testis. 42 99

Qualitative histochemical G6PDH distribution patterns obtained in the liver acinus of adult male and female rats with an improved method (Rieder et al., 1978) served as a basis for the isolation by microdissection of tissue samples of defined zonal affiliation. G6PDH activity was assayed quantitatively in tissue samples of zones 1 and 3 by a microfluorometric method, using the oil well technique and enzymatic cycling (Burch et al., 1963; Lowry and Passonneau, 1972). With the use of a correlation system further evidence could be presented for the validity of the recently described qualitative distribution patterns. From a total of 50 analyzed tissue samples the following G6PDH activities were calculated: 4.25 +/- 1.56 U/g dry weight in zone 1 and 2.08 +/- 0.46 U/g dry weight in zone 3 of male and 7.21 +/- 1.03 U/g dry weight in zone 1 and 11.10 +/- 2.56 U/g dry weight in zone 3 of female rats. These data were corrected for interference from the G6PDH activity of the Kupffer cells within zone 1 samples (approximately 80 U/g dry weight), so that the actual relative values for the parenchymal activity could be estimated for the first time: 2 U/g dry weight in zones 1 and 3 of male animals, 5 U/g dry weight in zone 1 and 11 U/g dry weight in zone 3 of female animals. In female livers G6PDH activity in zone 1 is therefore 2.5 times higher, and in zone 3 5 times higher than in the male. These zonal as well as sex-differences are clearly indicative of a heterogeneous functional organization of the liver acinus in terms of capacity for NADPH production, mainly in connection with reductive reactions in fatty acid synthesis.
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PMID:NADP-dependent dehydrogenases in rat liver parenchyma. II. Comparison of qualitative and quantitative G6PDH distribution patterns with particular reference to sex differences. 42 12

Glucose-6-phosphate dehydrogenase was purified to homogeneity from testes and kidneys of the inbred strain of mice (DBA/2J) by a simple two-step affinity column procedure. This involved the sequential application of 8-(6-aminohexyl)-amino-AMP- and -2', 5'-ADP-Sepharose columns and biospecific elution with NADP+ in both steps. The molecular and biochemical properties of the purified enzyme were studied in detail. These include the molecular weight determination, amino acid composition, steady-state kinetics, inactivation by high temperature, urea and iodoacetate, and immunology. The purified enzyme from mouse kidneys or testes was shown to be a tetramer with a molecular weight of 220,000. The enzyme is highly specific for glucose-6-phosphate, exhibits almost no activity with NAD+ as a coenzyme and is little inhibited by AMP or ATP. Michaelis constants for glucose-6-phosphate and NADP+ were determined to be 50 microM and 10 microM respectively. NADPH is a competitive inhibitor of NADP+ and has a Ki of 18 microM. Rabbit antisera against glucose-6-phosphate dehydrogenase were raised. The antisera also cross-react with the same enzyme from human and guinea pig.
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PMID:Purification and characterization of mouse glucose 6-phosphate dehydrogenase. 46 Jan 73

Mycotoxic porcine nephropathy was induced by p.o. administration of crystalline ochratoxin A for periods of 5 days, 3 months and 2 years. Enzyme activities of the renal tissue were studied histochemically. These were NADH-tetrazolium reductase, NADPH-tetrazolium reductase, lactate dehydrogenase, isocitrate dehydrogenase, succinate dehydrogenase, glucose-6-phosphate dehydrogenase, alpha-glycerophosphate dehydrogenase, unspecific acid phosphatase and unspecific alkaline phosphatase. The activity of NADH-tetrazolium reductase and succinate dehydrogenase was reduced in the proximal tubule of all nephrons after 5 days ochratoxin A exposure and remained reduced after 3 months and 2 years exposure. The effect of ochratoxin A on these enzymes would appear to cause the impairment of proximal tubular function and the morphological changes observed in the proximal tubule in ochratoxin A-induced mycotoxic porcine nephropathy. The localization of alterations in enzyme activity corresponds to the localization of ochratoxin A previously demonstrated in the kidney. The activities of NADPH-tetrazolium reductase, lactate dehydrogenase, glucose-6-phosphate dehydrogenase and unspecific alkaline phosphatase were reduced focally corresponding to the areas with focal tubular atrophy and the degree of reduction was roughly parallel to the degree of atrophy.
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PMID:Ochratoxin A-induced mycotoxic porcine nephropathy: alterations in enzyme activity in tubular cells. 47 26

The ultrastructural localization of glucose-6-phosphate dehydrogenase (NADP-linked) has been attempted in steroid-secreting cells. Rat adrenocortical cells and newt testicular glandular cells were fixed in an ice-cold mixture of 1% methanol-free formaldehyde and 0.25% glutaraldehyde. Potassium ferricyanide was used as the final electron acceptor. After incubation, the final copper ferrocyanide precipitate is exclusively observed in the hyaloplasm of these cells, provided that an electron carrier (1.0 mM PMS) has been added to the medium in order to by-pass the tissue "diaphorase" (NADPH-ferricyanide reductase) reaction. No precipitate appears in the absence of glucose-6-phosphate (substrate). Incubation in a medium devoid of PMS results in an exclusively mitochondrial reaction; the latter is that of the "diaphorase", which in these cells is mitochondrial. These results prove the importance of utilizing exogenous electron carriers (such as PMS) in coenzyme-linked dehydrogenase cytochemistry. Although polyvinyl alcohol was included in the washing and incubation media, in order to increase their viscosity, problems still exist concerning ultracytochemical localization of this "soluble" enzyme; these problems are discussed in the paper.
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PMID:Ultrastructural demonstration of glucose-6-phosphate dehydrogenase activity in steroid-secreting cells. 50 Apr 6


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