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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. The existence of two different D-glucose-6-phosphate dehydrogenases in Pseudomonas fluorescens has been demonstrated. Based on their different specificity and their different metabolic regulation one enzyme is appointed to the Entner-Doudoroff pathway and the other to the hexose monophosphate pathway. 2. A procedure is described for the isolation of that D-glucose-6-phosphate dehydrogenase which forms part of the Entner-Doudoroff pathway (Entner-Doudoroff enzyme). A 950-fold purification was achieved with an overall yield of 44%. The final preparation, having a specific activity of about 300 mumol NADH formed per min per mg protein, was shown to be homogeneous. 3. The molecular weight of the Entner-Doudoroff enzyme has been determined to be 220000 by gel permeation chromatography, and that of the other enzyme (Zwischenferment) has been shown to be 265000. 4. The pI of the Entner-Doudoroff enzyme has been shown to be 5.24 and that of the Zwischenferment 4.27. The Entner-Doudoroff enzyme is stable in the range of pH 6 to 10.5 and shows its maximal activity at pH 8.9. 5. The Entner-Doudoroff enzyme showed specificity for NAD+ as well as for NADP+ and exhibited homotropic effects for D-glucose 6-phosphate. It is inhibited by ATP which acts as a negative allosteric effector. Other nucleoside triphosphates as well as ADP are also inhibitory. 6. The enzyme catalyzes the transfer of the axial hydrogen at carbon-1 of beta-D-glucopyranose 6-phosphate to the si face of carbon-4 of the nicotinamide ring and must be classified as B-side stereospecific dehydrogenase.
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PMID:D-glucose-6-phosphate dehydrogenase (Entner-Doudoroff enzyme) from Pseudomonas fluorescens. Purification, properties and regulation. 0 Dec 57

The molar absorptivity of NADH at 340 nm has been determined by an indirect procedure in which high-purity glucose is phosphorylated by ATP in the presence of hexokinase, coupled to oxidation of the glucose-6-phosphate by NAD+ in the presence of glucose-6-phosphate dehydrogenase. The average value from 85 independent determinations is 6317 liter mol-1 cm-1 at 25 degrees C and pH 7.8. The overall uncertainty is -4.0 to +5.5 ppt (6292 to 6352 liter mol-1 cm-1), based on a standard error of the mean of 0.48 ppt and an estimate of systematic error of -2.6 to +4.1 ppt. Effects of pH, buffer, and temperature on the molar absorptivity are also reported.
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PMID:Determination of the molar absorptivity of NADH. 0 88

Electrophoretic analysis of glucose 6-phosphate dehydrogenase from liver and blood of rainbow trout revealed a complex series of bands, which could differ between fish. The partial interconvertible nature of these bands was demonstrated with enzyme that had been incompletely inactivated at pH 8.4. In a single population of 40 fish, a homozygote and a heterozygote for an electrophoretic variant allele were found. We suggest that G6PD in rainbow trout liver and blood is determinted by two alleles at a single locus, with posttranslational modification responsible for the complex electrophoretic patterns seen. The basis for this variation appears to be NADH binding to the protein molecule. Another variant and other properties of the enzyme are described.
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PMID:Glucose 6-phosphate dehydrogenase in rainbow trout. 0 63

Glucose-6-phosphate dehydrogenase (D-glucose-6-phosphate : NADP+ L-oxidoreductase EC 1.1.1.49) isolated from Paracoccus denitrificans grown on glucose/nitrate exhibits both NAD+-and NADP+- linked activities. Both activities have a pH optimum of pH 9.6 (Glycine/NaOH buffer) and neither demonstrates a Mg2+ requirement. Kinetics for both NAD(P)+ and glucose-6-phosphate were investigated. Phosphoenolpyruvate inhibits both activities in a competitive manner with respect to glucose-6-phosphate. ATP inhibits the NAD+-linked activity competitively with respect to glucose-6-phosphate but has no effect on the NADP+-linked activity. Neither of the two activities are inhibited by 100 muM NADH but both are inhibited by NADPH. The NAD+-linked activity is far more sensitive to inhibition by NADPH than the NADP+-linked activity.
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PMID:Metabolic regulation of the glucose-6-phosphate dehydrogenase from Paracoccus denitrifcans grown on glucose/nitrate. 1 31

Zoogloea ramigera I-16 M was found to contain two stereospecific acetoacetyl CoA reductases; one was NADP+-linked and D(-)-beta-hydroxybutyryl CoA specific and the other was NAD+-linked and L(+)-isomer specific. The NADP+-linked enzyme, purified approximately 150-fold, had a pH optimum for the reduction of acetoacetyl CoA at 8.1, but no definite pH optimum for the oxidation for beta-hydroxybutyryl CoA. The apparent Michaelis constants for acetoacetyl CoA and NADPH were 8.3 and 21 micrometer, respectively. The enzyme was markedly inhibited by acetoacetyl CoA at concentrations higher than 10 micrometer. The incorporation of [1-14C]acetyl CoA into poly-beta-hydroxybutyrate (PHB) by bacterial crude extract (containing beta-ketothiolase, acetoacetyl CoA reductases, enoyl CoA hydratases and PHB synthases) or by a system reconstituted from purified preparations of beta-ketothiolase, acetoacetyl CoA reductase and PHB synthase, was observed only in the presence of NADPH, but not NADH. Among various enzymes involved in PHB metabolism, only the specific activity of glucose 6-phosphate dehydrogenase was elevated 5-fold within 2 h after the addition of glucose to the cells grown in the basal medium. These findings suggest that, in Z. ramigera I-16M, acetoacetyl CoA is directly reduced to D(-)-beta-hydroxybutyryl CoA by the NADP+-dependent reductase, and PHB synthesis is at least partially controled by NADPH availability through glucose 6-phosphate dehydrogenase.
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PMID:An NADP-linked acetoacetyl CoA reductase from Zoogloea ramigera. 2 Aug 66

A method is described which enables one to assay simultaneously the NAD- and NADP-linked reactions of dehydrogenases which can utilize both coenzymes. The method is based on the fact that the thionicotinamide analogs of NADH and NADPH absorb light maximally at 400 nm, a wavelength sufficiently far removed from the absorbance maximum of NADH and NADPH to permit measurements of the simultaneous reduction of NAD+ (or NADP+) and the thionicotinamide analog of NADP+ (or NAD+). Application of the method to glucose-6-phosphate dehydrogenase from Leuconostoc mesenteroides reveals differential effects of glucose 6-phosphate concentration on the NAD- and NADP-linked reactions catalyzed by this enzyme which can not be detected by conventional assay procedures and which may have regulatory significance.
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PMID:Simultaneous analysis of NAD- and NADP-linked activities of dual nucleotide-specific dehydrogenases. Application to Leuconostoc mesenteroides glucose-6-phosphate dehydrogenase. 3 41

Human adult lung fragments removed from macroscopically undamaged and anthracosis exempted zones of lungs of 20 pneumonectomies made for cancer, were tested for 25 enzymic activities. The location and intensities of these enzymic activities were different in the lung tissue components; The bronchial epithelia contained highly active LDH, MDH, SDH, NADH-TR and NADPH-TR, glucose-6-phosphate dehydrogenase, active hydroxyproline-2-epimerase, alkaline phosphatase. Ca2+-activated ATP-ase, and beta-galactosidase. Bronchial and vascular muscles presented intense activities of LDH, MDH and SDH of alkalinephosphatase, AMP-ase and Ca2+-activated ATP-ase, as well as of beta-galactosidase. The alveolar walls presented high activities of SDH, MDH and LDH, of alkaline and acid phosphatases, of beta-galactosidase and of Tween-40 and 60-esterases, of HEP, cytochrome-oxidase and peroxidase. The free alveolar macrophages were active for LDH, MDH, SDH, NADH-TR and NADPH-TR, G1-6-ph-DH, acid and alkaline phosphatase, cytochrome-oxidase and peroxidase, HEP, AMP-ase and Mg2+-activated ATP-ase, Tween-esterases, naphthol-ASD-acetate esterase, and beta-galactosidase. The endothelia contained high activities of alkaline phosphatase, of AMP-ase and Mg2+-activated ATPase, of LDH, MDH and SDH, and of beta-galactosidase. In bronchial lymphoid nodules it was the LDH, MDH, SDH, cytochrome-oxidase and peroxidase, HEP, alkaline phosphatase and AMP-ase, Tween-60-esterase and beta-galactosidase that were active. The interlobular areas of the lung presented intense activities of SDH, MDH, LDH, HEP and cytochrome-oxidase. The activities of the other tested enzymes were weaker or absent in the adult human lung components, the same as those of aminopeptidases which were present only in some free alveolar macrophages. The discussion of some relationships between these enzymic actitivies and the morphology of the human adult lung tissue asserted that the latter could not be considered as a "normal" tissue but as one overstrained by the components of blood and polluted air.
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PMID:Histoenzymology of the lung. I. Enzyme activities of the lung tissue of acult humans; relationships between structure and functions. 14 Mar 14

A study of post-mortem changes in human central nervous tissue has shown that within 100 h of death, no significant change occurs in the amount of nerve cell DNA and nucleolar RNA nor in some membrane-associated enzymes such as succinate dehydrogenase, NADH and NADPH diaphorase, and cytochrome oxidase. Low molecular weight RNA species, probably transfer and messenger RNA are quickly lost, but there is little alteration in ribosomal RNA content. Cytoplasmic enzymes show variable changes; phosphofructokinase activity is rapidly decreased; hexokinase is unaltered but lactate dehydrogenase, pyruvate kinase and glucose-6-phosphate dehydrogenase initially show increases in activity which subsequently decline. Oxygen uptake diminishes quickly. These findings indicate that mechanical alterations in cell structure, following death, render organelles physiologically ineffective long before any significant changes in certain constituent biochemicals are detected. This report emphasizes the great importance necessary in the selection of appropriately time matched post-mortem tissues if accurate comparative studies of many of the cells constituents are to be made.
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PMID:Post-mortem changes in human central nervous tissue and the effects on quantitation of nucleic acids and enzymes. 14 55

Using the puberal rat and the PMS-treated rat as animal systems, ovarian events associated with follicular and luteal development have been characterized by measuring gonadotrophic hormone (LH, FSH and prolactin) and progesterone concentrations in peripheral serum; and selected enzymic (NAD-kinase:NAD-K and glucose-6-phosphate dehydrogenase: G6PD) activities and nucleotide (NAD, NADH, NADP, NADPH, ATP) concentrations in ovarian tissue. In the puberal rat, the period of follicular development was characterized by increased ovarian NAD-K SA, NAD and NADH concentrations and decreased ATP and NADP concentrations. The first pro-oestrus was characterized by greatly elevated LH, FSH, prolactin and progesterone concentrations, significant decreases in ovarian NAD-K SA, NAD, NADP and ATP concentrations, and an increase in NADPH concentrations. The development of new corpora lutea was associated with striking increases in ovarian NAD-K SA and G6PD SA. Increased activity of both enzymes exhibited a significant positive coefficient of correlation with the number of corpora lutea contained within the ovarian tissue. PMS (4 IU) stimulation of follicular activity resulted in events leading to the induction of an endogenous LH surge and ovulation. Associated with increased follicular activity was increased ovarian NAD-K SA. In contrast to the puberal rat, no rise in progesterone concentrations was associated with the LH surge or the formation of corpora lutea.
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PMID:Follicular and luteal function in the puberal rat: gonadotrophic hormone stimulation and enzymic-nucleotide interactions. 23 61

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


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