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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)

Glucose-6-phosphate dehydrogenase from Leuconostoc mesenteroides is irreversibly inactivated by the 2,3'-dialdehyde of NADP+ (oNADP+) in the absence of substrate. The inactivation is first order with respect to NADP+ concentration and follows saturation kinetics, indicating that the enzyme initially forms a reversible complex with the inhibitor followed by covalent modification (KI = 1.8 mM). NADP+ and NAD+ protect the enzyme from inactivation by oNADP+. The pK of inactivation is 8.1. oNADP+ is an effective coenzyme in assays of glucose-6-phosphate dehydrogenase (Km = 200 microM). Kinetic evidence and binding studies with [14C] oNADP+ indicate that one molecule of oNADP+ binds per subunit of glucose-6-phosphate dehydrogenase when the enzyme is completely inactivated. The interaction between oNADP+ and the enzyme does not generate a Schiff's base, or a conjugated Schiff's base, but the data are consistent with the formation of a dihydroxymorpholino derivative.
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PMID:Modification of glucose-6-phosphate dehydrogenase from Leuconostoc mesenteroides with the 2',3'-dialdehyde derivative of NADP+ (oNADP+). 380 18

A fluorimetric procedure for the determination of phosphoglycerate kinase in single human hair follicles is described. Enzyme studies on different parts of hair follicles after dissection show that the distribution of glucose-6-phosphate dehydrogenase matches that of phosphoglycerate kinase. Glucose-6-phosphate dehydrogenase can therefore be used as a reference enzyme to compensate for differences in hair follicle sizes. It was shown that the variation in the values found in individual hair follicles is improved by relating phosphoglycerate kinase to glucose-6-phosphate dehydrogenase activity. In areas of the world where glucose-6-phosphate dehydrogenase deficiency occurs frequently, an autosomally inherited reference enzyme may be preferred. It is shown that 6-phosphogluconate dehydrogenase is useful in this respect. Upon storage a gradual drop in the activity of all three enzymes was observed, but the rate of decrease was about equal: the enzyme activity ratio was, therefore, almost unaffected for a period of one week. This allows the determination of phosphoglycerate kinase even in mailed hair follicles.
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PMID:Phosphoglycerate kinase deficiency: biochemical studies on hair follicles. 380 12

Glucose-6-phosphate dehydrogenase catalyzes the initial and rate-limiting step of the pathway that is the principal source of NADPH in many cells. Earlier studies of cells from several species indicated that the intracellular enzyme is under severe and unexplained restraint or inhibition. Moreover, the intracellular enzyme of human erythrocytes exhibits sigmoid kinetics, whereas the purified enzyme exhibits only classical kinetics. We here report that most of the NADP in the human erythrocyte is bound by soluble proteins. In addition, the fraction of unbound NADP that is in the oxidized form, [NADP+]/[NADP], varies in a sigmoid manner relative to the fraction of bound NADP that is in the oxidized form. These features of intracellular binding of NADP: 1) account for the previously unexplained inhibition and sigmoid kinetics of glucose-6-phosphate dehydrogenase within human erythrocytes and 2) represent a system in which activity of a rate-limiting enzyme is largely determined by the binding and release of substrate and product by intracellular proteins other than the enzyme itself.
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PMID:NADP-binding proteins causing reduced availability and sigmoid release of NADP+ in human erythrocytes. 394 1

Glucose-6-phosphate dehydrogenase and N-acetyl-beta-glucosaminidase activities were both elevated after eccentric exercise indicating that this type of exercise causes muscle damage. Muscle damage as measured by glucose-6-phosphate dehydrogenase activity in the vastus intermedius was greater and occurred later in larger rats indicating that the susceptibility to muscle damage is increased and the repair process delayed in older and larger animals.
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PMID:The susceptibility to exercise-induced muscle damage increases as rats grow larger. 399 32

The presence of cloned methionyl human growth hormone at 1 microgram/ml medium for the final 5 days of a 6-day culture period decreased the activity of malic enzyme (EC 1.1.1.40) 45% from 202 to 112, fatty acid synthetase 52% from 26 to 12, and ATP citrate lyase (EC 4.1.3.8) 20% from 192 to 154 nmol NADPH.min-1.mg-1 supernatant protein in rat hepatocytes maintained in serum-free primary culture. Also, the activity of mitochondrial glycerol-3-phosphate dehydrogenase (EC 1.1.99.5) decreased 52% from 20 to 9 nmol.min-1.mg-1 mitochondrial protein. In the same cells, no changes were observed in the activity of 6-phosphogluconate dehydrogenase (EC 1.1.1.44) and lactate dehydrogenase (EC 1.1.1.27). Glucose-6-phosphate dehydrogenase (EC 1.1.1.49) was increased 2.4-fold from 70 to 183 nmol.min-1.mg-1 protein, indicating the activity of this enzyme was paradoxically increased, whereas other enzymes involved in lipogenesis were decreased. Half-maximal decrease of malic enzyme activity and increase of glucose-6-phosphate dehydrogenase activity occurred at 10 and 3 ng methionyl human growth hormone per milliliter medium, respectively. These values are within the range of normal circulating growth hormone concentrations in the rat. The effects on malic enzyme and glucose-6-phosphate dehydrogenase appeared after 3-day exposure to growth hormone. These findings are consistent with the hypothesis that growth hormone antagonizes the action of agents that stimulate the activity of malic enzyme while concomitantly increasing the extractable activity of glucose-6-phosphate dehydrogenase.
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PMID:Effects of growth hormone on lipogenic enzyme activities in cultured rat hepatocytes. 400 44

Cytoplasmic activities of NADP-linked malic enzyme (E.C. 1.1.1.40), glucose-6-phosphate dehydrogenase (E.C. 1.1.1.49) and NADP-linked isocitrate dehydrogenase (E.C. 1.1.1.42) were determined in tissues of selected avian species, and compared with those in mammals. Malic enzyme was generally more active in avian liver and kidney than in the corresponding mammalian tissues. Hepatic activities as high as 200 units/g wet wt and 100 units/g wet wt were recorded in the Nectariniidae and the Ploceidae respectively. Glucose-6-phosphate dehydrogenase was generally less active in avian tissues than malic enzyme. In passerine birds activities were very low indeed, and in most cases spectrophotometrically undetectable. Malic enzyme and glucose-6-phosphate dehydrogenase were highly active in the adipose tissue of mammals but were inactive in the adipose tissue of birds. Marked increases in hepatic malic enzyme and glucose-6-phosphate dehydrogenase activities were associated in birds with premigratory fattening. Activities of isocitrate dehydrogenase were comparable in the corresponding avian and mammalian tissues, including adipose tissue.
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PMID:Cytoplasmic NADP-linked dehydrogenase activities in avian tissues. 402 87

Glucose-6-phosphate dehydrogenase activity increases following denervation of rat skeletal muscle. The specificity of this effect to muscle fibre type was studied. Basal activity of the dehydrogenase was higher in soleus, a muscle composed predominantly of type I fibres, than in extensor digitorum longus, a muscle composed predominantly of type IIa and b fibres. The enzymatic activity of the soleus was also greater than that of the red (RQ) and white (WQ) portions of quadriceps muscle (predominantly type IIa and type IIb fibres, respectively). Following denervation, glucose-6-phosphate dehydrogenase increased in extensor digitorum longus and RQ, but not in WQ or the soleus. Following chronic treatment of rats with 3,3',5-triiodothyronine, which converts type I muscle fibres to type II, the dehydrogenase activity increased in both denervated soleus and extensor digitorum longus. It is concluded that the effect of denervation on glucose-6-phosphate dehydrogenase activity is selective for type IIa (fast oxidative-glycolytic) muscle fibres.
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PMID:Fibre-type specificity and effect of thyroid hormone on glucose 6-phosphate dehydrogenase activity in normal and denervated skeletal muscles of the rat. 403 Mar 97

Glucose-6-phosphate dehydrogenase (D-glucose-6-phosphate: NADP+ 1-oxidoreductase, EC 1.1.1.49) from the thermophilic bacteria, Bacillus stearothermophilus, was purified and its properties were examined. The enzyme was shown to consist of four identical subunits, each of about Mr 50,000. This enzyme utilized both NADP+ and NAD+ as cofactors, and the maximum velocity for both cofactors was similar. However, the Km values were quite different from each other, being 0.016 and 1.64 mM for NADP+ and NAD+, respectively. From the analysis of sulfhydryl groups it was shown that there is one sulfhydryl group and one disulfide bridge per subunit. This sulfhydryl group had no reactivity with 5,5'-dithiobis(2-nitrobenzoic acid) in the absence of guanidine hydrochloride. The enzyme showed a remarkable thermostability as well as storage stability.
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PMID:Purification and properties of glucose-6-phosphate dehydrogenase from Bacillus stearothermophilus. 405 54

Histochemical enzymatic studies were performed on 30 freshly resected large bowel carcinomas, 30 samples of normal colonic epithelium, and six samples of the histologically normal epithelium (so-called transitional epithelium) immediately adjacent to a carcinoma. Five enzymes were studied: nicotine adenine dinucleotide tetrazolium reductase (NADH-TR), glucose-6-phosphate dehydrogenase, succinate dehydrogenase, monoamine oxidase, and acid phosphatase. QUANTITATIVE AND QUALITATIVE DIFFERENCES IN ENZYME ACTIVITY WERE OBSERVED BETWEEN NORMAL, TRANSITIONAL, AND CARCINOMATOUS MUCOSA AS FOLLOWS: monoamine oxidase activity was moderate in normal mucosa, high in transitional mucosa, and low in carcinoma. Succinate dehydrogenase activity was high in transitional mucosa and low or moderate in normal and carcinomatous mucosa. Glucose-6-phosphate dehydrogenase activity showed a gradation from low in normal mucosa to high in carcinoma while acid phosphatase showed the reverse of this pattern. The tetrazolium reductase activity was low or moderate in normal and transitional mucosa and high in carcinoma. These differences in enzyme activity and their possible clinical and metabolic significance are discussed.
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PMID:An investigation into the enzyme histochemistry of adenocarcinomas of human large intestine and of the transitional epithelium immediately adjacent to them. 415 40

Extracts of Pseudomonas aeruginosa (ATCC 7700) cells grown on glucose, gluconate, or glycerol had enzyme activities related to the Entner-Doudoroff pathway. These activities were present in no more than trace amounts when the bacteria were grown on succinate. Fructose-1,6-diphosphate aldolase could not be detected in extracts of the bacteria grown on any of the above carbon sources. Therefore, it appears that P. aeruginosa degrades glucose via an inducible Entner-Doudoroff pathway. The apparent absence of fructose-1,6-diphosphate aldolase in cells growing on succinate suggests that the bacteria can form hexose and pentose phosphates from succinate by an alternate route. d-Glucose-6-phosphate dehydrogenase, a branch-point enzyme of the Entner-Doudoroff pathway, was purified 50-fold from glucose-grown cells. Its molecular weight, estimated by sucrose density gradient centrifugation, was found to be approximately 190,000. The enzyme was strongly inhibited by adenosine triphosphate, guanosine triphosphate, and deoxyguanosine triphosphate, which decreased the apparent binding of glucose-6-phosphate to the enzyme. It is suggested that adenine nucleotide-linked control of glucose-6-phosphate dehydrogenase may regulate the overall catabolism of hexose phosphates and prevent their wasteful degradation under certain conditions requiring gluconeogenesis.
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PMID:Adenosine triphosphate-linked control of Pseudomonas aeruginosa glucose-6-phosphate dehydrogenase. 438 49


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