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)

The dynamic properties of a series of in vitro reaction systems with increasing complexity and containing phosphofructokinase as central enzyme have been investigated. An experimental strategy and a principal mathematical treatment was elaborated to search for the minimum requirements with respect to the enzyme composition of a reaction system for generating limit cycle behaviour. As a criterion, such models have been developed which permit experimental realization by application of a specially designed flow-through equipment. In addition to phosphofructokinase, the following enzymes have been stepwise included into the reaction systems composing the Models 1 through 6: pyruvate kinase, adenylate kinase, hexokinase, and glucose 6-phosphate isomerase. It turned out that only a minimum dynamic system containing phosphofructokinase and pyruvate kinase as well as excesses of adenylate kinase and glucose 6-phosphate isomerase for maintaining equilibrium conditions between the respective reacting species, acquires the property of limit cycle behaviour and, hence, to generate sustained self-oscillations. The approach permits to compute the region of the experimentally variable parameters (influx rates of fructose 6-phosphate and ATP, maximum rate of pyruvate kianse) for which self-oscillatory behaviour can be predicted.
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PMID:Dynamic properties of in vitro enzyme systems containing phosphofructokinase. 15 82

Cow red cells, under in vitro incubation conditions, exhibit a comparatively low glycolytic rate of 0.56 +/- 0.05 micromol/(ml cells.h), with a ratio of lactate formed to glucose consumed of 1.58. It has been found that this low glycolytic rate can be stimulated 50--60% above the basal level in the presence of a variety of purine and pyrimidine compounds including adenosine, inosine, adenine, hypoxanthine, xanthine, and uracil. In contrast, calf red cells, which have a much higher glycolytic rate, display no discernible response to these agents. In attempts to elucidate the mechanism by which this stimulation takes place, both glucose transport and glycolytic enzyme activities were determined in the presence of these stimulators. Glucose influx in cow red cells, measured using the glucose analog 3-O-methyl-glucose, exhibits both a low Km of 117 microM and a Vmax of 0.38 micromol/(ml cells.min), and is unaltered in the presence of adenosine. On the other hand, hexokinase, which in normal hemolysates of cow red cells has an activity of 0.49 +/- 0.03 micromol/(g Hb.min). was found to be stimulated to 0.73 micromol/(g Hb.min) in the presence of adenine. Both pyruvate kinase and phosphofructokinase were unaffected by this compound. These data suggest that certain purines and pyrimidine compounds may exert their stimulatory effect on hexokinase activity, resulting in an augmentation of cow red cell glycolysis.
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PMID:Cow red blood cells. I. Effect of purines, pyrimidines, and nucleosides in bovine red cell glycolysis. 15 91

The activity of the following enzymes was studied in normal, precancerous, and malignant biopsies from the human cervix uteri: hexokinase (HK), phosphofructokinase (PFK), pyruvate-kinase (PK), lactate dehydrogenase (LDH), and glucose-6-phosphate dehydrogenase (G-6-PDH). In precancerous conditions, i.e., dysplasia and carcinoma in situ without any signs of invasive carcinoma, only PK showed moderate but significant activity increases. A rise in enzyme activity in biopsies histologically classified as carcinoma in situ was found to signal the presence of invasive carcinoma in other parts of the cervix. In invasive carcinomas of the cervix, all the enzymes studied showed a two- to four-fold increase (p less than 0.01) as compared to the normal cervix. The present study failed to reveal significant differences between enzyme activities in biopsies from patients in Stage I, II, and III; no correlation could be established between enzyme activity and prognosis.
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PMID:The glycolytic enzyme activity of the human cervix uteri. 16 34

The effect of an antitumor antibiotic bruneomycin on the energy metabolism in the liver tissue was studied. Four hours after the drug administration the consumption of glycogen and glucose in the liver tissue increased because of glycogenolysis activation, which was evident from increased activity of prosphorylase, phosphofructokinase, hexokinase and summation glycolytic activity. 24 and 48 hours after the antibiotic administration the balance of consumption and resynthesis of phosphate macroergs in the liver tissue impaired, which was evident from decreased levels of ATP, impairement of conjugation of the processes of oxidation due to impairement of permeability and structural integrity of the mitochondrial membranes. Further decrease in the glycogen liver levels was mainly due to suppressed resynthesis of glycogen because of destructive-necrotic processes. Simultaneously the processes of glycolytic splitting of glucose decreased which was evident from decreased activity of the enzymes and summation glycolytic activity.
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PMID:[Experimental effect of bruneomycin on the energy metabolism of liver tissue]. 16 20

1. The ratio of the combined activities of hexokinase (EC 2.7.1.1) and glucokinase (EC 2.7.1.2) to the activity of glucose-6-phosphatase (EC 3.1.3.9) changed in favour of the glycolytic enzymes during pregnancy and at peak lactation. 2. There were no important changes in the ratio of the activity of phosphofructokinase (EC 2.7.1.11) to that of fructose diphosphatase (EC 3.1.3.11). 3. The ratio of the activity of pyruvate kinase (EC 2.7.1.40) to the combined activities of phosphoenolpyruvate carboxylase (EE 4.1.1.32) and pyruvate carboxylase (EC 6.4.1.1) changed in favour of the glycolytic enzyme during pregnancy and at peak lactation, but changed in favour of the gluconeogenic enzymes immediately after parturition. 4. These changes are considered in relation to the changes in food intake and hormonal status that occur during pregnancy and lactation.
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PMID:The effects of pregnancy and lactation on the activities in rat liver of some enzymes associated with glucose metabolism. 17 Sep 98

The activities (Vmax) of hexokinase, glycogen phosphorylase, glucose-6-phosphate dehydrogenase, phosphofructokinase, lactate dehydrogenase, citrate synthase, cytochrome c oxidase, and 3-OH-acyl-CoA dehydrogenase in human skeletal muscles were compared with the in vitro utilization of glucose and palmitic acid assessed under optimal conditions. Statistically significant correlations between substrate fluxes and enzyme activities were found suggesting that the substrate incorporation rate in vitro in some way reflects the capacity of metabolic pathways. The incorporation rate of leucine into muscle proteins was also statistically significantly correlated to the RNA concentration in the muscle tissue. Glycolytic and glycogenolytic enzymes correlated significantly to each other and correlations were also found between aerobic enzymes supporting the validity of constant proportions between certain key enzymes in human skeletal muscles.
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PMID:Incorporation rate of glucose carbon, palmitate carbon and leucine carbon into metabolites in relation to enzyme activities and RNA levels in human skeletal muscles. 17 28

In our studies of metabolic control mechanisms in skeletal muscle from rhesus fetus we have determined the tissue levels of the metabolic intermediates and cofactors of the glycolytic pathway and have calculated the mass-action ratios for each reaction. Skeletal muscle from rhesus fetuses (Macaca mulatta), 90-155 days of gestational age, and from adult rhesus monkeys was used in these experiments. The apparent equilibrium constants for hexokinase and phosphofructokinase (PFK) in these tissues were over 1,000 times larger than the mass-action ratios at all ages studied; the corresponding values for pyruvate kinase were more than 800 times different. The data suggest that these three enzymes are rate-limiting for fetal skeletal muscle as early as 54% of gestation. The next step was to study some of the numerous factors that modify these non-equilibrium reactions. Increasing the ATP concentration had a marked effect on the PFK activity of both fetal and adult muscle, first increasing and then inhibiting enzyme activity. At maximum PFK activity, the amount of fructose-6-PO4(F6P) phosphorylated per mg of protein was 2-3 times greater in the two fetal than in the adult series. At a concentration of 0.3 mM, citrate decreased PFK activity of the 100-day fetal muscle; a further decrease occurred at 1.2 mM citrate. At a citrate level of 0.3 mM. the addition of inorganic phosphate (Pi) or cyclic AMP returned PFK activity to the uninhibited levels (pH 7.0). Relief of ATP inhibition of F6P phosphorylation with Pi and cyclic AMP was also observed at pH 7.0 in extracts of 100-day fetal skeletal muscle.
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PMID:Control of glycolysis in skeletal muscle from fetal rhesus monkeys. 17 43

1. Procedures were developed for the extraction and assay of glycolytic enzymes from the epididymis and epididymal spermatozoa of the rat. 2. The epididymis was separated into four segments for analysis. When rendered free of spermatozoa by efferent duct ligation, regional differences in enzyme activity were apparent. Phosphofructokinase, glycerol phosphate dehydrogenase and glucose 6-phosphate dehydrogenase were more active in the proximal regions of the epididymis, whereas hexokinase, lactate dehydrogenase and phosphorylase were more active in the distal segment. These enzymes were less active in the epididymis of castrated animals and less difference was apparent between the proximal and distal segments. However, the corpus epididymidis from castrated rats had lower activities of almost all enzymes compared with other epididymal segments. 3. Spermatozoa required sonication to obtain satisfactory enzyme release. Glycolytic enzymes were more active in spermatozoa than in epididymal tissue, being more than 10 times as active in the case of hexokinase, phosphoglycerate kinase and phosphoglycerate mutase. 4. The specific activities of a number of enzymes in the epididymis were dependent on the androgen status of the animal. These included hexokinase, phosphofructokinase, aldolase, glyceraldehyde phosphate dehydrogenase, phosphoglycerate kinase, pyruvate kinase, glycerol phosphate dehydrogenase, glucose 6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and phosphorylase. 5. The caput and cauda epididymidis differed in the extent to which enzyme activities changed in response to an altered androgen status. The most notable examples were hexokinase, phosphofructokinase, aldolase, phosphoglycerate kinase, 6-phosphogluconate dehydrogenase and phosphorylase.
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PMID:Activity and androgenic control of glycolytic enzymes in the epididymis and epididymal spermatozoa of the rat. 18 56

The action of free fatty acids on glycolytic enzymes was compared in normal and neoplastic tissues. Preincubation of tissue supernatant fractions with octanoate or laurate caused an inhibition of the activities of hexokinase and phosphofructokinase. An inhibition was also observed of lactate production with either glucose or glucose 6-phosphate as substrate. A similar degree of inhibition was observed for actions on normal liver and kidney, on the 7800 and 3924-A hepatomas and on the MK-3 renal cortical tumor. The possible relationship between the inhibition of glycolytic enzymes by fatty acids and anti-tumor activity previously observed with these compounds was noted.
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PMID:Inhibition of glycolytic enzymes of rat liver and hepatomas by free fatty acids. 19 94

The activities of hexokinase, glucokinase, phosphofructokinase, glucose-6-phosphate dehydrogenase, glucose-6-phosphatase, and fructose-1,6-diphosphatase were determined in loach embryos developed in solutions of insulin, hydrocortisone, estrone and thyroxin at different stages of embryogenesis. Glucokinase and fructose-1,6-diphosphatase activties are shown not to change markedly under the influence of the above-mentioned hormones. During some periods of early development the hexokinase activity is inhibited by insulin, estrone and thyroxin. The glucose-6-phosphate dehydrogenase activity is suppressed by each of the used hormones at all the stages of early embryogenesis while the glocose-6-phosphatase activity decreased only under the influence of insulin at the cleavage, blastula and gastrula stages. Insulin increased the activity of phosphofructokinase at the cleavage, blastula and early gastrula stages and hydrocortisone, estrone and thyroxine during certain periods of these stages. From middle gastrula two last hormones decreased the phosphofructokinase activity in the loach embryos.
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PMID:[Activity of carbohydrate metabolism enzymes in loach embryos under the influence of hormones]. 19 80


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