Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.1.1 (hexokinase)
 5,274 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A general hypothesis is presented for the decline in the rate of ethanol production (per unit of cell protein) during batch fermentation. Inhibition of ethanol production is proposed to result from the intracellular accumulation of AMP during the transition from growth to the stationary phase. AMP acts as a competitive inhibitor of hexokinase with respect to ATP. When assayed in vitro in the presence of ATP and AMP concentrations equivalent to those within cells at different stages of fermentation, hexokinase activity declined in parallel with the in vivo decline in the rate of ethanol production. The coupling of glycolytic flux and fermentation to cell growth via degradation products of RNA may be of evolutionary advantage for Saccharomyces cerevisiae. Such a coupling would reduce the exposure of nongrowing cells to potentially harmful concentrations of waste products from metabolism and would conserve nutrients for future growth under more favorable conditions.
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PMID:Intracellular accumulation of AMP as a cause for the decline in rate of ethanol production by Saccharomyces cerevisiae during batch fermentation. 327 91

Rat hepatocytes were cultured in a modified HI-WO/BA medium for 13 days, and the combined effect of dexamethasone, 10(-7) M, insulin, 10(-8) M, and glucagon, 10(-9) M on the DNA-content, and on the activity of several enzymes, the secretion of albumin and the rate of ethanol oxidation was investigated. The effect of ethanol on these parameters was also studied. All parameters measured declined with time in the hormone-free cultures. In hormone-supplemented cultures, the DNA-content, the activity of glucokinase, pyruvate kinase, hexokinase and lactate dehydrogenase and the secretion of albumin was maintained at reasonable levels throughout the 13 days, whereas both the activity of alcohol dehydrogenase and the rate of ethanol oxidation fell significantly, although less than in hormone-free cultures. Addition of 50 mM ethanol to the hormone-supplemented culture medium caused a ca. 20% fall in the activity of glucokinase and pyruvate kinase and a 20% increase in alcohol dehydrogenase activity. No effect of ethanol was observed on the activity of hexokinase and lactate dehydrogenase or on the secretion of albumin.
Alcohol Alcohol Suppl 1987
PMID:Long-term culture of hepatocytes: ethanol oxidation and effect of ethanol on enzyme activities and albumin secretion. 332 6

Incubation of Saccharomyces cerevisiae with xylose and ethanol for 16 hours leads to a decrease of hexokinase (and glucokinase) activity in the cells. It does not alter the levels of polyphosphate, orthophosphate and ATP. The transport of the glucose derivative 2-deoxy-D-glucose, a sugar that can be phosphorylated, is inhibited after this treatment, whereas transport of 6-deoxy-D-glucose, which has a blocked phosphorylation site, is not inhibited. Even though, both deoxyglucoses use the same transport system. The decrease in initial velocity of 2-deoxy-D-glucose transport is most pronounced under anaerobic conditions. Incubation of the cells with antimycin A, a treatment which has a similar effect as anaerobiosis, shows, that the inhibition of the transport of 2-deoxy-D-glucose is presumably the result of an increase in the Km of the carrier transport. Transport of glucose is probably regulated by kinase enzymes.
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PMID:Effect of xylose incubation on the glucose transport system in Saccharomyces cerevisiae. 353 51

Whereas glucose is a major substrate for pulmonary lipid synthesis, fructose has also been suggested as a potential substrate. In vivo pulmonary fatty acid synthesis is depressed in hormonally deprived conditions, such as diabetes, and this can be modified by fructose feeding, but not by glucose feeding. In this study the glucose and fructose utilizations were compared in normal, diabetic and fasting states using isolated perfused rat lungs. When (U-14C)- or (5-3H)-glucose was used as substrate, glucose utilization by lung was reduced by 50% in both the fasting and diabetic animals compared to the normal controls. Using (U-14C)-glucose as substrate, the incorporation of (14C)-label in various metabolites of glucose was significantly depressed. For example, this reduction was 50% in lactate, pyruvate and CO2, 15% in ethanol-insoluble fraction, 65% in neutral lipids, 75% in phospholipids, 80% in fatty acid moiety, 40% in deacylated fraction and 10% in the polysaccharide fractions. Refeeding the fasted animals or insulin treatment to the diabetic animals restored these depressed (14C)-recoveries to the normal levels. Fructose utilization was less than 10% of glucose utilization, but remained unaffected by fasting and diabetic states. In addition, pulmonary hexokinase enzyme activity was lowered significantly in fasting and diabetic animals, whereas fructokinase enzyme activity was not altered. Despite the low rate of fructose utilization, these results suggest that fructose may serve as an alternative substrate for pulmonary phospholipid synthesis when glucose utilization is significantly depressed.
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PMID:Nutritional and hormonal control of glucose and fructose utilization by lung. 390 22

Three glucose-phosphorylating enzymes were separated from cell-free extracts of Saccharomyces cerevisiae by hydroxylapatite chromatography. Variations in the amounts of these enzymes in cells growing on glucose and on ethanol showed that hexokinase PI was a constitutive enzyme, whereas synthesis of hexokinase PII and glucokinase were regulated by the carbon source used. Glucokinase proved to be a glucomannokinase with Km values of 0.04 mM for both glucose and mannose. D-Xylose produced an irreversible inactivation of the three glucose-phosphorylating enzymes depending on the presence or absence of ATP. Hexokinase PI inactivation required ATP, while hexokinase PII was inactivated by D-xylose without ATP in the reaction mixture. Glucokinase was protected by ATP from this inactivation. D-Xylose acted as a competitive inhibitor of hexokinase PI and glucokinase and as a non-competitive inhibitor of hexokinase PII.
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PMID:Inhibition and inactivation of glucose-phosphorylating enzymes from Saccharomyces cerevisiae by D-xylose. 390 28

1. Enzymic evidence supporting the operation of the Entner-Doudoroff pathway in the anaerobic conversion of glucose into ethanol and carbon dioxide by Zymomonas mobilis is presented. 2. Cell extracts catalysed the formation of equimolar amounts of pyruvate and glyceraldehyde 3-phosphate from 6-phosphogluconate. Evidence that 3-deoxy-2-oxo-6-phosphogluconate is an intermediate in this conversion was obtained. 3. Cell extracts of the organism contained the following enzymes: glucose 6-phosphate dehydrogenase (active with NAD and NADP), ethanol dehydrogenase (active with NAD), glyceraldehyde 3-phosphate dehydrogenase (active with NAD), hexokinase, gluconokinase, glucose dehydrogenase and pyruvate decarboxylase. Extracts also catalysed the overall conversion of glycerate 3-phosphate into pyruvate in the presence of ADP. 4. Gluconate dehydrogenase, fructose 1,6-diphosphate aldolase and NAD-NADP transhydrogenase were not detected. 5. It is suggested that NAD is the physiological electron carrier in the balanced oxidation-reduction involved in ethanol formation.
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PMID:The route of ethanol formation in Zymomonas mobilis. 428 42

Rats preferring ethanol were distinct from water-consuming animals in a decreased level of immunoreactive insulin im blood serum as well as in glucokinase activity of liver tissue. Per oral loading with glucose, 4 g/kg of body mass, enabled to detect a difference in the sugar phosphorylation via hexokinase and glucokinase reactions as well as the dissimilar sensitivity of the insulin system to glucose in the ethanol-, water-consuming and intermediate animals. Ethanol-consuming rats were more resistant to the effect of starvation during 48 hrs. The data obtained suggest that the characteristic properties of glucose metabolism in ethanol-consuming rats appear to be responsible for increased consumption of ethanol, which is used as optimal energy source, metabolized via pathways which did not involve the glycolytic pathway.
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PMID:[Characteristics of glucose metabolism in rats with different preferences for alcohol]. 609 27

Cells of the aerotolerant anaerobe Giardia lamblia respire in the presence of oxygen. Endogenous respiration is stimulated by glucose but not by other carbohydrates and Krebs cycle intermediates. Endogenous and glucose-stimulated respiration are insensitive to cyanide, malonate, and 2,4-dinitrophenol, but are inhibited by atabrin and iodoacetamide. G. lamblia produces ethanol, acetate and CO2 both aerobically and anaerobically either from endogenous reserves or exogenous glucose. Molecular hydrogen is not produced. The following enzyme activities were detected in homogenates: hexokinase, fructose-biphosphate aldolase, pyruvate kinase, phosphoenolpyruvate carboxykinase, malate dehydrogenase, malate dehydrogenase (decarboxylating), pyruvate synthase, acetyl-CoA synthetase, alcohol dehydrogenase (NADP+), NADH dehydrogenase, NADPH dehydrogenase, NADPH oxidoreductase and superoxide dismutase. The enzymes of energy and carbohydrate metabolism are nonsedimentable (109 000 x g for 30 min). Activities of lactate dehydrogenase, hydrogenase, phosphate acetyltransferase, acetate kinase, citrate synthase, succinate dehydrogenase, fumarate hydratase and catalase were below the limits of detection. The results suggest the occurrence of glycolysis, energy production by substrate level phosphorylation and a flavin, iron-sulfur protein mediated electron transport system as well as the absence of cytochrome mediated oxidative phosphorylation and functional Krebs cycle.
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PMID:Energy metabolism of the anaerobic protozoon Giardia lamblia. 610 7

The spectra and activities of isozymes of hexokinase and alcohol dehydrogenase (enzymes that catalyse glucose and ethanol assimilation), glucose-6-phosphate dehydrogenase (the key enzyme of the pentose phosphate shunt) and malate dehydrogenase (an enzyme of the tricarboxylic acid cycle) were comparatively studied in Pichia pinus haploid (MH4) and autodiploid (D4) strains. Differences in the qualitative composition of the isoenzyme spectra and activities suggest that the intensity and the role of the studied metabolic pathways and cycles differ between the haploid and autodiploid strains of Pichia pinus.
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PMID:[Comparative study of the spectra and activities of isoenzymes in haploid and autodiploid strains of Pichia pinus]. 634 87

The object of this work was to study the activity and the isozyme spectra of hexokinase (the triggering enzyme of glycolysis), glucose-6-phosphate dehydrogenase (the key enzyme of the pentose-phosphate shunt), malate dehydrogenase and isocitrate dehydrogenase (the enzymes of the citric acid cycle) and alcohol dehydrogenase (the enzyme involved in the first steps of ethanol oxidation) in Saccharomyces cerevisiae, race Ya, S. carlsbergensis, race 4228, and their hybrid 67. The parent organisms and their hybrid were shown to differ from one another in the qualitative composition and the activity of the isozyme spectra of the above enzymes.
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PMID:[Component activity of the isoenzyme spectra of Saccharomyces cerevisiae, Saccharomyces carlsbergensis and their hybrids]. 636 88


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