Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

Muscle biopsies were obtained from three cyclists and four runners at the end of 10-24 mo of intensive training and after intervals of detraining up to 12 wk. Control samples came from four untrained persons and four former athletes. Macro mixed fiber samples were assayed for lactate dehydrogenase, adenylate kinase, glycogen phosphorylase, citrate synthase, malate dehydrogenase, beta-hydroxyacyl-CoA dehydrogenase, succinate dehydrogenase, beta-hydroxybutyrate dehydrogenase, creatine kinase, hexokinase, 1-phosphofructokinase, fructosebisphosphatase, protein, and total creatine. In the case of three trained persons and two controls, the first six of the enzymes were also measured in individual fibers. Before detraining, enzymes of oxidative metabolism were substantially higher than in controls, and differences in levels between type I and type II fibers were smaller. During detraining, oxidative enzymes were decreased in both fiber types but the type II fibers did not fall to control levels even after 12 wk. Phosphorylase increased with detraining in both fiber types. The same is true for lactate dehydrogenase and adenylate kinase, except in the case of the type I fibers of one individual. Among the other six enzymes (measured in mixed fiber samples), only hexokinase was consistently affected (decreased) by detraining.
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PMID:Effects of detraining on enzymes of energy metabolism in individual human muscle fibers. 682 50

The effect of daily intraperitoneal administration of Mn2+(4 mg/kg) was investigated on the metabolism of carbohydrates and certain enzymes involved in the oxidation of glucose in the rat liver and blood at the intervals of 30, 60 and 90 days after exposure. Mn2+ had no effect on the contents of blood reducing sugars and proteins, however the levels of pyruvic and lactic acids were reduced at 60 and 90 days after the metal treatment. The contents of liver glycogen and proteins remained unaffected while pyruvic acid content was decreased in Mn2+ treated rat liver throughout the experimental period. The activities of glycogen phosphorylase and lactate dehydrogenase decreased while that of phosphoglucoisomerase and glucose-6-phosphatase increased in the post mitochondrial supernatant at 60 and 90 days of Mn2+ exposure. The levels of hexokinase decreased and FDP-aldolase and fructose-1, 6-diphosphatase increased throughout the experimental period. The magnitude of alteration was found to be greater with the increase in the duration of Mn2+ treatment. Several of the mitochondrial enzymes in the liver were inhibited in the manganese exposed rats which may be responsible to inhibit the rate of dehydrogenation of Kreb cycle's intermediates along with the linked respiratory chain and eventually oxidation in the rat liver.
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PMID:Effects of manganese on carbohydrate metabolism and mitochondrial enzymes in rats. 713 26

Mouse renal cell tumors (RCTs) were induced in male CBA mice by 5 subcutaneous injections of 8 mg 1,2-dimethylhydrazine (DMH)/kg body weight once a week. After a lag period of 2 yr kidneys were removed, and serial cryostat sections of the kidneys were histochemically analyzed for the following parameters: glycogen content, basophilia, and the activities of glycogen synthase (SYN), glycogen phosphorylase (PHO), glucose-6-phosphatase (G6Pase), glucose-6-phosphate dehydrogenase (G6PDH), hexokinase (HK), pyruvate kinase (PK), lactate dehydrogenase (LDH), malic enzyme (ME), succinate dehydrogenase (SDH), alkaline phosphatase (ALPase) and gamma-glutamyltranspeptidase (GGT). RCTs displayed the same histochemical profile irrespective of their size and growth pattern. In comparison with the normal kidney epithelium, the neoplastic cells exhibited elevated activities of enzymes for glycolysis (HK, PK, LDH) and the pentose phosphate pathway (G6PDH), while negative G6Pase and low SDH activity were observed in these cells. The majority of RCTs showed high PHO activity and weak staining for SYN. Activities of ALPase and GGT were negative in most of the RCTs. Markedly enlarged cells with atypical nuclei were detected in some advanced RCTs. Higher activities of glycolytic and mitochondrial enzymes and G6PDH were found in these enlarged cells than in other tumor cells. Tubular preneoplastic lesions were similar to neoplastic lesions in morphological and histochemical characteristics. The present study revealed that a markedly elevated capacity for glycolysis and the pentose phosphate pathway occurred in RCTs in mice. A similar histochemical pattern in the few preneoplastic tubular lesions observed suggests that these metabolic aberrations emerge early during carcinogenesis, but additional studies on early stages of renal carcinogenesis are needed to substantiate this assumption.
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PMID:Enzymic pattern of preneoplastic and neoplastic lesions induced in the kidney of CBA mice by 1,2-dimethylhydrazine. 781 30

Selected enzymes were measured in mixed-fiber bundles and individual fibers from rat plantaris (PL) and soleus (Sol) muscles that had undergone either 2 wk of tetrodotoxin (TTX) inactivation of the sciatic nerve, a sham operation, or were contralateral to the TTX limb. TTX disuse caused severe wasting of PL (46%) and Sol (26%) muscles and of single fibers (50% and 40%, respectively). TTX PL and Sol also had reduced (50%) glycogen content. In TTX, PL, and Sol macro samples and single fibers, the activities (mol.h-1.kg dry wt-1) of hexokinase, glycogen phosphorylase, and lactate dehydrogenase were higher, lower, and unchanged, respectively, compared with controls. Single-fiber data showed that these changes occurred in all fibers. In TTX PL macro samples, activities of glycerol-3-phosphate dehydrogenase (GPDH), pyruvate kinase (PK), malate dehydrogenase (MDH), citrate synthase (CS), beta-hydroxyacyl-CoA dehydrogenase (BOAC), and thiolase were, or tended to be, lower. Single-fiber data showed a disappearance of high-oxidative moderate glycolytic fibers (i.e., usually fast-twitch oxidative in control) and the appearance of more fibers with a metabolic enzyme profile approaching that of control slow-oxidative fibers. In TTX Sol macro samples, GPDH and PK tended to be higher, and thiolase, BOAC, CS, and MDH lower. Single-fiber data corroborated these findings and suggested the appearance of fast fibers with downregulated oxidative enzyme profiles. Our results suggest that neuromuscular activity is a major, but not the sole, determinant of the size and metabolic heterogeneity that exists in muscle cells.
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PMID:Effects of tetrodotoxin-induced neural inactivation on single muscle fiber metabolic enzymes. 804 92

A slab gel electrophoresis apparatus with the ability to operate over a pressure range of 10(-3) to 2 kbar is described. The system presented here is an improvement of a previous apparatus (A. A. Paladini, J. L. Silva, and G. Weber, Anal. Biochem. 161, 358-364, 1987). It consists of a flat bed gel, with a significantly enlarged buffer reservoir, which eliminates the requirement of high concentrations of running buffers, and at the same time allows shorter runs, leading to enhanced resolution and reproducibility. The application of the method to the dissociation of the tetramer glycogen phosphorylase a as a function of hydrostatic pressure is described. The flat geometry of the apparatus allows for the first time the analysis of the stability of oligomers and their constituent subunits to chemical denaturation by urea gradient electrophoresis gels at high pressure. Dimeric hexokinase shows a reversible cooperative unfolding transition with a midpoint at 3.8 M urea. In contrast, the monomers unfold at very low urea concentration (< 1.0 M). The observed differences in stability validates oligomerization as an important stabilizing element of the protein structure.
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PMID:Analysis of dissociation and unfolding of oligomeric proteins using a flat bed gel electrophoresis at high pressure. 807 94

In the presence of glycogen, ADP, phosphoglucomutase and hexokinase, the glycogen phosphorylase b activity associated to sarcoplasmic reticulum (SR) membranes stimulates Ca2+ uptake by SR membrane fragments in the absence of added ATP. Phosphoglucomutase and hexokinase lead to the formation of glucose 6-phosphate which in turn is used as an ATP regenerating system by the Ca2+ pump. It is proposed that a raise of cytosolic AMP and ADP concentrations after muscle contraction can activate an alternative metabolic route which would be used to ensure the maintenance of a low cytosolic Ca2+ concentration and avoid unnecessary metabolic energy depletion in muscle cells.
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PMID:Glycogen phosphorolysis can form a metabolic shuttle to support Ca2+ uptake by sarcoplasmic reticulum membranes in skeletal muscle. 825 Aug 71

A method was developed to measure the activities of enzymes in extracts from single human preimplantation embryos. The method permits the analysis of two enzymes plus appropriate controls in an extract from a single embryo, and was used to investigate the control of energy metabolism during the development of human embryos from the two-cell to the blastocyst stage. Hexokinase (HK), 6-phosphofructokinase (PFK), pyruvate kinase (PK), fructose-1,6-diphosphate aldolase (ALD), glucose phosphate isomerase (GPI), lactate dehydrogenase (LDH), glucose-6-phosphate dehydrogenase (G6PDH) and 2-oxoglutarate dehydrogenase (ODH) were all detectable, whereas glycogen phosphorylase (GP) was not. The enzyme activities of ODH, PFK, LDH, PK, GPI and G6PDH, averaged over all stages of development from the two-cell to blastocyst stage (days 2-6 after insemination), were 3.5, 6.6, 15, 69, 73 and 87 times greater than HK, respectively. The activity of ALD was very similar to that of HK. The activities of ALD, GPI, PFK, PK and LDH showed no significant variation with stage of development, although the activity of GPI fell significantly from the four-eight cell to the eight-sixteen cell stage (P < 0.05). HK activity decreased from the two-eight cell to the eight-sixteen cell (P < 0.05), and increased significantly from the eight-sixteen cell to the blastocyst stage (P < 0.01). The overall relationship between hexokinase activity and stage approached significance (P = 0.059, one-way analysis of variance). The activity of G6PDH decreased significantly with development (P < 0.001, one way analysis of variance).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Activity of enzymes of energy metabolism in single human preimplantation embryos. 828 48

A line of transgenic mice was constructed in which the human Glut1 glucose transporter is overexpressed in skeletal muscle. Overexpression of Glut1 protein was evident in epitrochlearis, extensor digitorum longus (EDL), and quadriceps muscles, and resulted in 6.6-7.4-fold elevations in basal glucose transport activity as measured in isolated muscles in vitro. The elevated glucose transporter activity in the skeletal muscles of transgenic mice was associated with a 10-fold increase in glycogen concentration in EDL and quadriceps muscles that was not due to an increase in muscle glycogen synthase activity or a decrease in glycogen phosphorylase activity. The increased glucose transport activity also resulted in a 2-fold increase in muscle lactate concentration, with no increase in muscle glucose 6-phosphate. Despite a slight (10%) increase in muscle hexokinase activity, there was a 4-fold increase in total muscle free glucose in transgenic mice, indicating that hexokinase becomes rate-limiting for glucose uptake when the rate of glucose transport is very high. These results demonstrate that the muscle glycogen content can be dramatically elevated by increasing the muscle Glut1 protein level and that glucose transport is a rate-limiting step for muscle glucose disposal in normal, resting mice.
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PMID:Evidence from transgenic mice that glucose transport is rate-limiting for glycogen deposition and glycolysis in skeletal muscle. 834 95

The presence of glycogen in astroglia-rich primary cultures derived from the brains of newborn rats depends on the availability of glucose in the culture medium. On glucose deprivation, glycogen vanishes from the astroglial cultures. This decrease of glycogen content is completely prevented if 2-deoxyglucose in a concentration of > 1 mM or 1,5-gluconolactone (20 mM) is present in the culture medium. 2-Deoxyglucose itself or 3-O-methylglucose, a glucose derivative that is not phosphorylated by hexokinase, does not reduce the activity of glycogen phosphorylase purified from bovine brain or in the homogenate of astroglia-rich rat primary cultures. In contrast, deoxyglucose-6-phosphate strongly inhibits the glycogen phosphorylase activities of the preparations. Half-maximal effects were obtained at deoxyglucose-6-phosphate concentrations of 0.75 (phosphorylase a, astroglial culture), 5 (phosphorylase b, astroglial culture), 2 (phosphorylase a, bovine brain), or 9 mM (phosphorylase b, bovine brain). Thus, the block of glycogen degradation in these cells appears to be due to inhibition of glycogen phosphorylase by deoxyglucose-6-phosphate rather than deoxyglucose itself. These results suggest that glucose-6-phosphate, rather than glucose, acts as a physiological negative feedback regulator of the brain isoenzyme of phosphorylase and thus of glycogen degradation in astrocytes.
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PMID:Inhibition by 2-deoxyglucose and 1,5-gluconolactone of glycogen mobilization in astroglia-rich primary cultures. 845 36

The effect of increased expression of glycogen phosphorylase on glucose metabolism in human muscle was examined in primary cultured fibers transduced with recombinant adenovirus AdCMV-MGP encoding muscle glycogen phosphorylase. Increments of 20-fold in total enzyme activity and of 14-fold of the active form of the enzyme were associated with a 30% reduction in basal glycogen levels. Total glycogen synthase activity was doubled in AdCMV-MGP-transduced cells even though the activity ratio was decreased. Incubation with forskolin, which inactivated glycogen synthase and activated glycogen phosphorylase, induced greater net glycogenolysis in engineered cells. In unstimulated fibers, lactate production was three times higher in AdCMV-MGP fibers as compared with controls, despite similar rates of glycogenolysis. In transduced fibers incubated with 2-deoxyglucose, the level of 2-deoxyglucose 6-phosphate was about 8-fold elevated over the control even though hexokinase activity was unmodified in AdCMV-MGP fibers. Overexpression of glycogen phosphorylase also led to enhancement of [U-14C]glucose incorporation into glycogen, lactate, and lipid. Accordingly, determination of lipid cell content revealed that engineered cells were accumulating lipids. Furthermore, 14CO2 formation from [U-14C]glucose was 1.6-fold higher, whereas 14CO2 formation from [6-14C]glucose was unmodified, in AdCMV-MGP fibers. Our data show that in human skeletal muscle cells in culture, the increase in glycogen phosphorylase activity is able to up-regulate glycogen synthase activity indicating the enhancement of glycogen turnover. We suggest that the increase in glycogen phosphorylase and, thereby, in glycogen metabolism, is sufficient to enhance glucose uptake in the muscle cell. Glucose taken up by engineered muscle cells is essentially disposed of through nonoxidative metabolism and converted into lactate and lipid.
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PMID:Overexpression of muscle glycogen phosphorylase in cultured human muscle fibers causes increased glucose consumption and nonoxidative disposal. 857 26


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