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)

As previously reported, during rabbit red blood cell aging glucose phosphorylating activities show several modifications. In the first period of the red cell life span the predominant form is similar to hexokinase II, while in the mature erythrocyte the predominant glucose phosphorylating activity resembles hexokinase I. In the oldest cells glucose phosphorylating activity has a low affinity (high Km) for glucose. In this paper the modifications of hexokinase in cell aging have been studied in vivo in a young erythrocyte population synchronized by actinomycin D, and in vitro in red cells separated in fractions according to different ages. Since protein synthesis is lacking in the mature red cell, we are inclined to explain the presence of low-affinity hexokinase activity in the oldest erythrocytes as an age-dependent transformation of a primary hexokinase.
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PMID:Decay pattern of rabbit erythrocyte hexokinase in cell aging. 4 84

Penicillin spheroplasts of Escherichia coli were ruptured osmotically, by freezing and thawing, or mechanically. Differential centrifugation sedimented 20-30% of the glycolytic enzymes without increasing their specific activities. There was, however, evidence of distinct groups of sedimenting enzymes; growth on different carbon sources could influence the distribution. Sucrose gradient studies gave no evidence of enzyme association but provided estimations of the molecular weight of each enzyme which were close to those subsequently observed on gel filtration. Using the determined molecular weight and a literature value for specific activity, the measured activity ratio of the enzymes was compared with that expected from an equimolar mixture. All values agreed within a factor of five, except for hexokinase. The relative roles of hexokinase and phosphotransferase in E. coli are briefly considered. An equimolar multienzyme aggregate of all the enzymes of glycolysis would have a molecular weight of about 1.6 X 10(6). Chromatography on a Biogel column yielded one fraction, corresponding to a molecular weight of 1.6 X 10(6), which contained a proportion of all the glycolytic enzyme studied; the remaining portion of each enzyme activity was eluted from the column at the position expected from its individual molecular weight. The fraction of mol. wt 1 600 000 was tested for complete glycolysis pathway activity and found not to be different from a reconcentrated mixture of the separated enzymes. Both the eluted and the reconstructed systems showed unexpected activity changes at different protein concentrations. The specific radioactivity of pyruvate formed by these systems from [14C]glucose 6-phosphate was reduced by the presence of unlabelled 3-phosphoglycerate, but by less than would have been expected had the latter been able to participate fully in glycolytic activity. This result indicates that these preparations were capable of selectivity compartmenting glycolytic intermediates. Electron microscope investigation of both systems showed large numbers of regular 30 nm diameter particles which, on disruption, appeared to be composed of smaller units: it is possible that these particles may have been aggregates containing glycolytic enzymes. The possible advantages of a glycolytic multienzyme complex are briefly discussed.
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PMID:The tentative identification in Escherichia coli of a multienzyme complex with glycolytic activity. 13

Adipose tissue and liver from vitamin B6-deficient rats have an increased lipogenic capacity. Whether this phenomenon is accompanied by changes in the activities of certain enzymes involved in the metabolism of carbohydrate and lipid, or by altered transport of glucose into adipocytes, has been studied. Five glycolytic enzymes (hexokinase, phosphoglucose isomerase, phosphofructokinase, aldolase, and pyruvate kinase), two pentose phosphate pathway enzymes (glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase), malic enzyme, and ATP citrate lyase were measured in the epididymal adipose tissue, livers and kidneys of vitamin B6-deficient and control rats. Vitamin B6 deficiency did not significantly affect the glycolytic enzyme levels in the tissues studied, or the dehydrogenases measured in adipose tissue and kidneys. Liver glucose-6-phosphate dehydrogenase, and adipose tissue and liver malic enzyme were significantly lowered in deficient rats compared to ad libitum and pair-fed controls. Adipose tissue and liver ATP citrate lyase activities were also significantly decreased by vitamin B6 deficiency. In the presence of insulin, the uptake of glucose and 3-O-methyl glucose, a non-metabolizable sugar, by fat pads from deficient rats was greater than uptake by fat pads from control rats. These observations suggest that the increased glucose utilization by adipose tissue and liver of vitamin B6-deficient rats is not directly related to changes in the enzymes studied, but in the case of adipose tissue, may be explained, at least in part, by enhanced glucose uptake.
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PMID:Effects of vitamin B6 deficiency on liver, kidney, and adipose tissue enzymes associated with carbohydrate and lipid metabolism, and on glucose uptake by rat epididymal adipose tissue. 13 63

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 activities of jejunal carbohydrate-metabolizing enzymes show adaptive drugs, and sex hormones. To learn whether insulin, tolbutamide, and glucagon had effects on these enzymes, we performed serial peroral jejunal biopsies in normal young men and in obese patients, before and after treatment with these agents. Jejunal mucosa was assayed for glycolytic enzyme activities, pyruvate kinase (PK), hexokinase (HK), and fructose-1,6-diphosphate aldolase (FDPA), and the nonglycolytic enzyme activity, fructose diphosphatase (FDPase). Insulin significantly increased the activity of jejunal PK (+48% change from control) and HK (+6%), decreased the activity of FDPase (-36%),and had no effect on FDPA. Glucagon had opposite effects; the activity of PK was decreased (-33%) and FDPase was increased (+50%). Tolbutamide significantly increased the activities of PK (+47%), HK (+14%), and FDPA (+7%), and decreased the activities of FDPase (-36%). The results of tolbutamide on glycolytic enzyme activities were independent of endogenous insulin. The data support the concept that jejunal carbohydrate-metabolizing enzymes in man respond to hormones and drugs similar to responses observed in rat liver. This is important because it now gives us a means of studying the actions of these hormones directly in human tissue.
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PMID:Effects of insulin, tolbutamide, and glucagon on activities of jejunal carbohydrate-metabolizing enzymes in humans. 16 65

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

This paper starts a series on red blood cell (RBC) metabolism in patients with chronic renal failure (CRF). The glycolytic enzyme levels and in vitro half-lives of these patients' RBCs were determined. A number of enzymes (hexokinase, glucose-6-phosphate isomerase, fructose-6-phosphate kinase, aldolase, glyceraldehyde-3-phosphate dehydrogenase and lactate dehydrogenase) showed higher activities than in normal control RBCs. Other enzyme activities were normal. These results were discussed and several possible mechanisms considered. We favour the point of view of a shortened life span of the RBCs in CRF, making the most unstable enzymes of the glycolytic sequence appear increase as compared with normal controls.
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PMID:Metabolism of red blood cells in chronic renal failure. I. Glycolytic enzyme levels. 22 98

Glucose phosphorylating activity of human erythrocytes quickly decreases during cell ageing; the electrophoretic pattern suggests that this fast decrease is due mainly to the isozyme II. We have shown that in the young cells only hexokinase I and II are responsible for the glucose phosphorylation, while in the old cells another glucose phosphorylating activity, more evident at high glucose concentration, is also present. The appearance of this activity during cell ageing could be interpreted as a post-translational modification of the native hexokinase.
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PMID:Relationship between glucose phosphorylating activities and erythrocyte age. 70

Three glucose-phosphorylating enzymes having different specificities for glucose and fructose were separated from the cell-free extract of Candida tropicalis by means of ammonium sulfate fractionation and chromatography on DEAE-cellulose and Sephadex G-100. Two of them, which phosphorylated fructose 1.5 times faster than glucose, were designated as hexokinase I and II (ATP : D-hexose 6-phosphotransferase, EC 2.7.1.1.), and the other with very low or no fructose-phosphorylating activity, as glucokinase (ATP : D-glucose 6-phosphotransferase, EC 2.7.1.2). Km values for glucose with both hexokinase I and glucokinase were 0.3 mM, and that for fructose with hexokinase I was 2.2 mM. Time-course changes in the levels of these enzymes in C. tropicalis growing on glucose and on n-alkane revealed that hexokinase was induced specifically by the sugars, while glucokinase was a constitutive enzyme. Addition of cycloheximide to the culture medium prevented the increase in the hexose-phosphorylating activity and in the Fru/Glu ratio (the ratio of enzymatic phosphorylation of fructose to that of glucose) in the cells. Although Candida lipolytica also contained hexokinase and glucokinase, both enzymes seemed to be constitutive.
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PMID:Glucose-phosphorylating enzymes of Candida yeasts and their regulation in vivo. 83 48

Human saliva was incubated with human enamel powder, and the lactoperoxidase activity of the saliva was measured before and after incubation. Liquidphase lactoperoxidase activity was reduced in direct proportion to the weight of enamel powder added. Lactoperoxidase molecules were adsorbed to the enamel surface in an enzymatically active conformation, and this enamel-bound lactoperoxidase activity was also measured. The adsorption of lactoperoxidase was irreversible and produced at least a 40% increase in the concentration of lactoperoxidase in the enamel surface phase as compared with its concentration in the liquid phase. Enamel-bound lactoperoxidase, as well as the free enzyme, was capable of inactivating the key glycolytic enzyme hexokinase. The implications of the adsorption phenomenon for bacterial colonization are discussed.
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PMID:Enzyme activity of salivary lactoperoxidase adsorbed to human enamel. 88 9


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