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)

A multifactorial quantitative analysis of oscillations in glycolysis was conducted in the postmicrosomal supernatant of rat muscle homogenates incubated in the presence of yeast hexokinase. Oscillations in adenine nucleotides, D-fructose 1,6-bisphosphate, triose phosphates, L-glycerol 3-phosphate, 3HOH generation from D-[5-3H]glucose, NADH and L-lactate production were documented. The occurrence of such oscillations were found to depend mainly on the balance between the consumption of ATP associated with the phosphorylation of D-glucose, as catalyzed by both yeast and muscle hexokinase, and the net production of ATP resulting from the further catabolism of D-fructose 6-phosphate, as initiated by activation of phosphofructokinase. The oscillatory pattern was suppressed in the presence of D-fructose 2,6-bisphosphate. It is proposed that the quantitative information gathered in this study may set the scene for further studies in extracts of cells other than myocytes, e.g. hepatocytes and pancreatic islet cells, in which no oscillation of glycolysis was so far observed.
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PMID:Oscillations in glycolysis: multifactorial quantitative analysis in muscle extract. 151 3

The activities of enzymes related to energy metabolism in the gastrocnemius and soleus muscles in young-adult (4 months), mature (12 months), and senescent (24 months) rats were compared after continuous (72 consecutive h) exposure to normobaric hypoxia or normoxia after the vasodilator naftidrofuryl or saline solution had been given intraperitoneally for 30 consecutive days. The maximum rats (Vmax) of the following enzyme activities in the crude extract and/or the crude mitochondrial fraction of each muscle specimen were evaluated for: the anaerobic glycolytic pathway (hexokinase, phosphofructokinase, pyruvate kinase, and lactate dehydrogenase), the tricarboxylic acid cycle (citrate synthase, and malate dehydrogenase), the electron transfer chain (cytochrome oxidase), and the NAD+/NADH redox state (total NADH cytochrome c reductase). The significance of differences between the enzyme activities at different ages or under different experimental conditions in the two tissue preparations of the two muscles were determined by ANOVA. MCA and ETA2 were used to evaluate the net effects of the experimental conditions. First, aging did not seem to affect the soleus and gastrocnemius muscles in the same way. In the gastrocnemius muscle, the major changes were seen in enzymes of the glycolytic pathway, in the crude extracts. In the soleus muscle, the more striking changes in enzyme activities as a function of aging were found in the crude mitochondrial fraction. We also found that hypoxia caused more important changes in 12-month-old rats than in those of other ages (especially the enzyme activities of the gastrocnemius muscle). Naftidrofuryl modified the effects of hypoxia only sometimes and further investigations are necessary before we can draw any conclusions about the pharmacological activity of naftidrofuryl in hypoxia.
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PMID:Effects of hypoxia and pharmacological treatment on enzyme activities in skeletal muscle of rats of different ages. 164 27

Enzyme histochemical profiles of spinal motoneurons in the zebrafish were determined. Five enzymes of glucose metabolism were chosen: glucose-6-phosphate dehydrogenase (G6PDH), hexokinase (HK), phosphofructokinase (PFK), succinate dehydrogenase (SDH) and NADH tetrazolium reductase (NADH-TR). Motoneurons were traced with Fluorogold and classified as those that innervate white muscle fibres (W-MNs) and those that innervate red and intermediate muscle fibres (R/I-MNs). The average enzyme activities per volume of tissue in the somata of both populations differed at most by 25%. Both the average soma volume and the average number of muscle fibres innervated are three times larger for the W-MNs than for the R/I-MNs. This suggests that the total amount of enzyme activity within a neuron soma matches target size. In the R/I-MNs, the activities of SDH and NADH-TR were closely correlated (correlation coefficient, r = 0.99; p less than 0.05) and HK activity correlated well with G6PDH activity (r = 0.94; p less than 0.05), but not with PFK (r = 0.64; p greater than 0.05). In the W-MNs, there was no correlation between SDH and NADH-TR (r = -0.59; p greater than 0.05) or between HK and G6PDH (r = 0.50; p greater than 0.05) and the correlation coefficient between HK and PFK activity was close to zero (r = 0.04; p greater than 0.05). It was concluded that in the R/I-MNs, which are continuously active, firing activity is fuelled by oxidative metabolism. We suggest that in the W-MNs glucose is stored in the form of glycogen and that, despite high levels of NADH-TR present, the energy for intermittent firing activity is provided by glycolysis.
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PMID:Histochemical profiles of motoneurons innervating muscle fibres with different activity patterns in the zebrafish, Brachydanio rerio. 183 17

The purpose of this work was to evaluate the biochemical changes in the myocardial cell using cardioplegia supplemented with creatine phosphate (CP). Many previous studies have demonstrated the beneficial effect of CP on the ischemic myocardium and its mechanism of action has been assumed to be mainly extracellular. Based on the assumption that CP could also exert some influence on myocardial cellular metabolism, this investigation was carried out. Forty patients undergoing mitral valve replacement were divided into two groups: group 1 was treated with standard cardioplegic solution, and group 2 was treated with cardioplegic solution enriched with CP at a concentration of 10 mmol/L. Samples of papillary muscle, obtained from the removed valve, were studied by means of biochemical methods in order to assess the enzyme activities and the metabolites of the different biochemical pathways related to energy metabolism in the myocardial cell. One papillary muscle sample was used to determine enzyme activities spectrophotometrically; another was used to evaluate metabolite concentrations by spectrophotometric or spectrophotofluorimetric methods. The rate of spontaneous functional recovery after rewarming and weaning from cardiopulmonary bypass (CPB) also was evaluated. In group 2, the Vmax of enzymatic activities was significantly greater (hexokinase, malate dehydrogenase, glutamate dehydrogenase, total NADH cytochrome c reductase) and a better functional state of the heart was observed after CPB. On the basis of the clinical and biochemical data, it is concluded that the myocardium was better preserved when CP was added to the cardioplegic solution. Therefore, the results suggest a possible interaction of exogenous CP with cellular metabolism.
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PMID:Biochemical changes induced in the myocardial cell during cardioplegic arrest supplemented with creatine phosphate. 193 52

Rats bearing the Walker-256 carcinosarcoma have a profoundly altered liver metabolite content with significant increases in the concentrations of glucose 6-phosphate, fructose 1,6-bisphosphate, citrate, lactate, and alanine, while the concentrations of glucose, pyruvate, dihydroxyacetone phosphate, and glutamine are decreased. As a result of these changes both the cytosolic NAD+/NADH ratio and the cytosolic phosphorylation potential are significantly lowered while no changes are detected in either the cytosolic NADP+/NADPH ratio or the mitochondrial NAD+/NADH ratio. These hepatic changes are accompanied by marked increases in the circulating concentrations of lactate, non-esterified fatty acids, and triacylglycerols. The activities of both liver hexokinase and phosphofructokinase are also significantly elevated in the tumor-bearing rats. The changes observed both in the redox state and phosphorylation potential are in agreement with the energy imbalance associated with tumor burden.
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PMID:The energy state of tumor-bearing rats. 199 70

Chemiluminometric methods are described for the automated flow injection analysis of NADPH and NADH using an immobilized enzyme column reactor and serum magnesium. This application is for the clinical analysis of NADPH and NADH. The reactor for NADPH and NADH contains immobilized L-glutamate dehydrogenase and L-glutamate oxidase, and that for serum magnesium immobilized hexokinase, glucose-6-phosphate dehydrogenase, L-glutamate dehydrogenase and L-glutamate oxidase. When the sample is introduced into the four-enzyme bioreactor, hydrogen peroxide is produced in proportion to the concentration of serum magnesium by the successive reactions. A co-immobilized hexokinase/glucose-6-phosphate dehydrogenase/glutamate dehydrogenase column reactor gave better efficiency compared with an enzyme column which was prepared by packing co-immobilized hexokinase/glucose-6-phosphate dehydrogenase and immobilized glutamate dehydrogenase to make two layers. Magnesium in serum was determined with 1 microL of the sample without carry-over and for an assay time of approximately 15 s. The present method is sensitive (detection limit 0.1 nmol) because Mg2+ is recycled in a column, and gives perfect linearity of the data up to 3.0 mmol/L with satisfactory precision, reproducibility, and accurate reaction recoveries.
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PMID:A chemiluminometric method for NADPH and NADH using a two-enzyme bioreactor and its application to the determination of magnesium in serum. 238 94

In order to investigate contributions by glucose metabolism via the Embden-Meyerhof pathway and that via the direct oxidation route to gluconate to initial ATP production during spore germination, respiratory activity and RNA synthesis were compared between the mutant lacking hexokinase and the parent spores of Bacillus megaterium QM B1551. We found that time courses of those metabolic events were almost identical between those spores, thus clearly indicating that NADH formed by a spore-specific enzyme glucose dehydrogenase (EC 1.1.1.47) is solely responsible for aerobic production of ATP at this stage.
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PMID:Glucose metabolism via the Embden-Meyerhof pathway is not involved in ATP production during spore germination of bacillus megaterium QM B1551. A study with a mutant lacking hexokinase. 245 May 41

The location of hexokinase at the surface of brain mitochondria was investigated by electron microscopy using immuno-gold labelling techniques. The enzyme was located where the two mitochondrial limiting membranes were opposed and contact sites were possible. Disruption of the outer membrane by digitonin did not remove bound hexokinase and creatine kinase from brain mitochondria, although the activity of outer membrane markers and adenylate kinase decreased, suggesting a preferential location of both enzymes in the contact sites. In agreement with that, a membrane fraction was isolated from osmotically lysed rat brain mitochondria in which hexokinase and creatine kinase were concentrated. The density of this kinase-rich fraction was specifically increased by immuno-gold labelling of hexokinase, allowing a further purification by density gradient centrifugation. The fraction was composed of inner and outer limiting membrane components as shown by the specific marker enzymes, succinate dehydrogenase and NADH-cytochrome-c-oxidase (rotenone insensitive). As reported earlier for the enriched contact site fraction of liver mitochondria the fraction from brain mitochondria contained a high activity of glutathione transferase and a low cholesterol concentration. Moreover, the contacts showed a higher Ca2+ binding capacity in comparison to outer and inner membrane fractions. This finding may have regulatory implications because glucose phosphorylation via hexokinase activated the active Ca2+ uptake system and inhibited the passive efflux, resulting in an increase of intramitochondrial Ca2+.
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PMID:Mitochondrial boundary membrane contact sites in brain: points of hexokinase and creatine kinase location, and control of Ca2+ transport. 245 93

Glyceraldehyde has been known to be an insulin secretagogue for more than 15 years. It has been (reasonably) assumed that glyceraldehyde enters the glycolytic pathway via its phosphorylation by ATP to form glyceraldehyde phosphate, a reaction catalyzed by the enzyme triokinase, and that subsequent metabolism is identical to that of glucose. glucose. However, up to now there have been no studies verifying the presence of triokinase in the pancreatic beta cell. We report here that (1) the activity of triokinase in pancreatic islets is very low, indicating that the activity is intrinsically low and/or the enzyme was rapidly inactivated during the preparation of tissue for assay; (2) the activity is much lower than glucose phosphorylating activity (hexokinase plus glucokinase) in islets, even though glyceraldehyde is a more efficient insulin secretagogue than glucose; (3) glyceraldehyde phosphate dehydrogenase from pancreatic islets can use glyceraldehyde as a substrate in place of glyceraldehyde phosphate (the Vmax of glyceraldehyde phosphate dehydrogenase from islets when glyceraldehyde is the substrate is 20-fold that of triokinase when glyceraldehyde is the substrate); and (4) the Km of glyceraldehyde phosphate dehydrogenase with respect to glyceraldehyde (4.8 mM) is similar to the concentration of glyceraldehyde that gives one-half maximal rates of insulin release from pancreatic islets, whereas the Km of triokinase with respect to glyceraldehyde is much lower (less than 50 microM). These data suggest that besides stimulating insulin release in islets via its entering metabolism by phosphorylation to glyceraldehyde phosphate in the triokinase reaction, glyceraldehyde could be phosphorylated by Pi in the glyceraldehyde phosphate dehydrogenase reaction to form glycerate 1-phosphate which is probably unmetabolizable in islets. The second reaction could drastically increase the NADH/NAD ratio in islets without providing substrates for hydrogen shuttles that reoxidize cytosolic NADH. Since an increased NAD(P)H/NAD(P) ratio is believed to be a key part of the signal for insulin release, such a mechanism would explain the potent insulinotropism of glyceraldehyde in short-term experiments. In addition, the formation of unmetabolizable acids may explain the toxic effects of long-term exposure of islets to glyceraldehyde and why glyceraldehyde causes the beta cell to become acidic, whereas glucose does not.
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PMID:Does glyceraldehyde enter pancreatic islet metabolism via both the triokinase and the glyceraldehyde phosphate dehydrogenase reactions? A study of these enzymes in islets. 253 42

In order to find the markers of the toxicity of the autoxidized lipids in the liver, rats were given a lethal amount of secondary autoxidation products of linoleic acid (400 mg/rat/day for 3 days) and then changes in the hepatic metabolic functions were analyzed. A decrease in acetyl-CoA level to half caused by the depletion of CoASH was reported in an associated paper (J. Nutr. Sci. Vitaminol., 35, 11-23, 1989). Citrate, isocitrate, and 2-oxoglutarate also decreased to half the level of those of the control group. Reduction in isocitrate dehydrogenase activity was only 25%, while NADH2 and ATP levels remained unchanged. Thus, the reduction in the citrate cycle activity was due to the decrease in acetyl-CoA. The activity of mitochondrial succinate dehydrogenase was decreased to 1/5. Other appreciable changes were depletion of glucose 6-phosphate and fructose 6-phosphate, accumulation of glucose 1-phosphate, reductions in hexokinase, phosphofructokinase, glucose-6-phosphatase, phosphoglucomutase, and phosphogluconate dehydrogenase activities, and decrease in the NADPH2 level. It was considered that these changes were caused by the depletion of glucose 6-phosphate whose synthetic pathways were abnormal. Therefore, the markers of the hepatotoxicity of secondary products were the changes in the CoASH level and the activities of succinate dehydrogenase and synthetic pathways for glucose 6-phosphate.
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PMID:Succinate dehydrogenase and synthetic pathways of glucose 6-phosphate are also the markers of the toxicity of orally administered secondary autoxidation products of linoleic acid in rat liver. 254 8


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