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)

1. This study examined the influence of pre-operative intravenous nutrition upon carbohydrate stores, glucose metabolism and protein synthesis in the liver of patients undergoing laparotomy. 2. Thirty patients with gastrointestinal cancer and weight loss (greater than 5 kg in 3 months) were randomized to receive a hospital diet only or a hospital diet plus intravenous nutrition (0.18 g of N + 125 kJ day-1 kg-1) for 3 or 7 days before laparotomy. Patients who had not lost weight received the hospital diet only and formed a control group. 3. Wedge biopsies of liver were obtained at laparotomy and analysed for glycogen concentration, the activity of three key enzymes of glucose metabolism, 6-phosphofructokinase (EC 2.7.1.11), fructose bisphosphatase (EC 3.1.3.11) and hexokinase (EC 2.7.1.1), and the capacity for protein synthesis. 4. Compared with controls and the hospital diet group, both phosphofructokinase and fructose bisphosphatase activity were reduced in patients who received intravenous nutrition, suggesting the utilization of glucose for glycogen synthesis with a reduction in the glycolytic flux. Consistent with these changes, patients who received intravenous nutrition had a significantly higher glycogen concentration compared with the control and hospital diet groups. 5. Maximal rates of protein synthesis were achieved after only 3 days of intravenous nutrition. 6. The provision of intravenous nutrition was associated with changes in hepatic metabolism suggestive of repletion of energy stores and a higher capacity for protein synthesis.
Clin Sci (Lond) 1989 Sep
PMID:Metabolic changes in human liver associated with preoperative intravenous nutrition. 255 26

The purified ATPase (F1F0) of Propionigenium modestum has its pH optimum at pH 7.0 or at pH 6.0 in the presence or absence of 5 mM NaCl, respectively. The activation by 5 mM NaCl was 12-fold at pH 7.0, 3.5-fold at pH 6.0, and 1.5-fold at pH 5.0. In addition to its function as a primary Na+ pump, the ATPase was capable of pumping protons. This activity was demonstrated with reconstituted proteoliposomes by the ATP-dependent quenching of the fluorescence of 9-amino-6-chloro-2-methoxyacridine. No delta pH was formed in the presence of the uncoupler carbonyl cyanide m-chlorophenylhydrazone or by blocking the ATPase with dicyclohexylcarbodiimide. In the presence of valinomycin and K+, the delta pH increased, in accord with the operation of an electrogenic proton pump. The proton pump was only operative at low Na+ concentrations (less than 1 mM), and its activity increased as the Na+ concentration decreased. Parallel to the decrease of H+ pumping, the velocity of the Na+ transport increased about 6-fold from 0.1 to 4 mM NaCl, indicating a switch from H+ to Na+ pumping, as the Na+ concentration increases. Due to proton leaks in the proteoliposomal membranes, fluorescence quenching was released after blocking the ATPase with dicyclohexylcarbodiimide, by trapping residual ATP with glucose and hexokinase, or by the Na+-induced conversion of the proton pump onto a Na+ pump. Amiloride, an inhibitor of various Na+-coupled transport systems, was without effect on the kinetics of Na+ transport by the P. modestum ATPase.
Biochemistry 1989 Sep 05
PMID:The sodium ion translocating adenosinetriphosphatase of Propionigenium modestum pumps protons at low sodium ion concentrations. 255 65

Addition of yeast hexokinase and glucose at various time points of the pre-mRNA splicing reaction rapidly depleted ATP and inhibited further progress of the reaction, indicating that ATP is required for both the first and second steps of splicing. ATP analogues, p-fluorosulfonylbenzoyl-5'-adenosine (FSBA) and 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl), which can modify amino acids at the ATP-binding site of a protein, inactivated the splicing activity of the nuclear extract. While the inactivation by the former was irreversible, the splicing activity was complemented by a Micrococcal nuclease-treated extract. This ATP analogue (FSBA) may be a useful tool for identification of ATP-dependent splicing factors.
J Biochem 1989 Sep
PMID:New methods to investigate ATP requirement for pre-mRNA splicing: inhibition by hexokinase/glucose or an ATP-binding site blocker. 260 92

The factors responsible for meal initiation in man are not known. Recently, a small, transient decline in blood glucose was found to precede meals in freely feeding rats (1). To determine whether a similar decline in blood glucose precedes meals in humans, we measured plasma glucose concentration before and after requests for lunch on 4 different days in each of 7 subjects living in a setting that eliminated temporal cues and most or all external prompts for eating. Under these conditions, subjects could request any meal at any time by naming it and specifying its content. Meals were promptly prepared and served. Blood was sampled at randomized intervals averaging 20 minutes. Blood samples from 120 minutes preceding the subject's request for lunch to 90 minutes after the request were analyzed for glucose by the hexokinase method. The mean plasma glucose concentration did not change significantly from about 1 hour before lunch request to 20-30 minutes after the request. A transient decline in glucose similar to that reported in the rat was observed prior to only 1 of the 28 lunches. Given the ease of obtaining food and the absence of the usual temporal and psychosocial cues for eating, the results are not consistent with the hypothesis that meal requests in humans are triggered by a transient decline of plasma glucose concentration. The hypothesis is not disproven, however, since the intersample intervals of about 20 minutes may have failed to detect decreases of blood glucose that were smaller or of shorter duration than those of the rat.
Physiol Behav 1989 Sep
PMID:Blood glucose prior to meal request in humans isolated from all temporal cues. 262 79

A simple and cheap one-step enzymatic method has been developed for the determination of 1-14C-glucose in plasma. C-1 of glucose is cleaved off as CO2 by treatment with hexokinase, glucose-6-phosphate dehydrogenase, and 6-phosphogluconic dehydrogenase. True 1-14C-glucose activity is then calculated as the difference between total radioactivity and radioactivity remaining after enzyme treatment and evaporation. The reaction is shown to be quantitative and specific, thus eliminating both labelled metabolites and label recycled to other positions in glucose. Two different types of pig experiments show that 1-14C-glucose, when determined by this method, is as irreversible a tracer as the commonly used 3-3H-glucose.
Diabetologia 1989 Sep
PMID:Enzymatic determination of 1-14C-glucose in pig plasma. 267 67

By using competition between glucose and its analogue D-glucosamine, we have produced a system in which it is possible to vary the steady-state growth rate of populations of Saccharomyces cerevisiae cells without otherwise altering the composition of the medium or significantly affecting catabolite repression. We demonstrate that D-glucosamine inhibits the accumulation of glucose derived label and the phosphorylation of glucose by hexokinase (EC 2.7.1.1).
J Gen Microbiol 1989 Sep
PMID:Controlling the growth rate of Saccharomyces cerevisiae cells using the glucose analogue D-glucosamine. 269 46

Previous analyses of glycolytic metabolites in Artemia embryos indicate that an acute inhibition of glucose phosphorylation occurs during pHi-mediated metabolic arrest under anoxia. We describe here kinetic features of hexokinase purified from brine shrimp embryos in an attempt to explain the molecular basis for this inhibition. At saturating concentrations of cosubstrate, ADP is an uncompetitive inhibitor toward glucose and a partial noncompetitive inhibitor toward ATP (Kis = 0.86 mM, Kii = 1.0 mM, Kid = 1.9 mM). With cosubstrates at subsaturating concentrations, the uncompetitive inhibition versus glucose becomes noncompetitive, while inhibition versus ATP remains partial noncompetitive. The partial noncompetitive inhibition of ADP versus ATP is characterized by a hyperbolic intercept replot. These product inhibition patterns are consistent with a random mechanism of enzyme action that follows the preferred order of glucose binding first and glucose-6-P dissociating last. We propose that inhibition by glucose-6-P (Kis = 65 microM) occurs primarily by competing with ATP at the active site, resulting in the formation of the dead-end complex, enzyme-glucose-glucose-6-P. Versus glucose, inhibition by glucose-6-P is uncompetitive at pH 8.0 and noncompetitive at pH 6.8. Over a physiologically relevant pH range of 8.0 to 6.8 alterations in Km and Ki values do not account for the reduction in glucose phosphorylation, and no evidence suggests that Artemia hexokinase activity is modulated by reversible binding to intracellular structures. Total aluminum in the embryos is 4.01 +/- 0.36 micrograms/g dry weight, or, based upon tissue hydration, 72 microM. This concentration of aluminum dramatically reduces enzyme activity at pH values less than 7.2, even in the presence of physiological metal ion chelators (citrate, phosphate). When pH, aluminum, citrate, phosphate, substrates, and products were maintained at cellular levels measured under anoxia, we can account for a 90% inhibition of hexokinase relative to activity under control (aerobic) conditions.
J Biol Chem 1989 Sep 15
PMID:Kinetic properties of hexokinase under near-physiological conditions. Relation to metabolic arrest in Artemia embryos during anoxia. 276 70

Glucose and lipid metabolism in the brain, liver and in a transplanted tumour were found to be variously altered within 2 to 3 h of administering single doses of the radiosensitizer Ro-03-8799 to normal and tumour-bearing mice. Hepatic lactate and glycerol-3-phosphate (G3P) levels were decreased but those of the ketone body beta-hydroxybutyrate (beta-HOBu) were raised. However, in the tumour, these levels were all enhanced. The lactate levels in brain remained relatively constant but both beta-HOBu and G3P levels were altered in a manner similar to that in the liver. The levels of glucose were approximately doubled in blood, brain and tumour, but whereas tumour G6P levels increased, those in the brain were lowered to below the limits of detection. Hepatic glucose levels were significantly decreased after 1 h but G6P levels were not affected. These changes could neither be related to inhibitory effects on hepatic glucokinase or brain hexokinase activity nor to limiting amounts of ATP in both tissues. However, the activity of glucose-6-phosphatase (G6P'ase) was distinctly raised in the liver and the hepatic glycogen stores were also rapidly lowered. Overall, the results suggest that Ro-03-8799 exerts a stimulatory effect on glucose production in the liver. In both liver and brain the levels of free fatty acids and phospholipids were increased whereas those of esterified fatty acids were lowered. Most importantly, the changes in metabolite levels affect the cellular redox couples; those of the cytosol (lactate/pyruvate; G3P/dihydroxyacetone phosphate (DAP] are directed towards the oxidised state in the liver but to a more reduced state in the tumour. The mitochondrial couple (beta-HOBu/acetoacetate (AcAc)) in both tissues is shifted towards the reduced state. These metabolic changes may result in an increase in the degree of hypoxia in the tumour and may well play an important role in the development of neuropathies.
Br J Cancer 1987 Sep
PMID:Effects on intermediary metabolism in mouse tissues by Ro-03-8799. 282 72

Mebendazole (3.3 mumol), causes in vitro glycogen depletion and inhibits glucose uptake in Avitellina lahorea. Inhibition of non-specific phosphomonoesterases and adenosine triphosphatase by mebendazole discussed in the light of the role of phosphatases in uptake mechanisms. Mebendazole has no effect on hexokinase which has broad substrate specificity but influences the activities of some glycolytic enzymes such as phosphorylase, phosphoglucomutase and glucose-6-phosphatase. Thus, it appears that mebendazole also acts to disrupt certain enzymes of carbohydrate metabolism which may ultimately cause death of the parasite.
J Helminthol 1987 Sep
PMID:In vitro effects of mebendazole on the carbohydrate metabolism of Avitellina lahorea (Cestoda). 282 93

Cytochemical and biochemical glucose 6-phosphatase (G6Pase) activity was examined in brown adipose tissues of normal, cold-exposed, or starved mice. In addition, G6Pase activity in white adipose tissue and hexokinase activity in brown and white adipose tissues were biochemically measured. In normal animals, the reaction product for G6Pase activity was localized in the endoplasmic reticulum and nuclear envelope of brown adipose cells. The amount of the reaction product increased in cold-exposed or starved animals. Biochemical G6Pase activity (259.7 +/- 48.5 ng Pi/min/mg protein) in brown adipose tissues of normal animals was higher when the value was compared with values of other organs. Biochemical G6Pase and hexokinase activities increased rapidly in brown adipose tissues of cold-exposed animals, and a close relation was found between activities of the two enzymes. In brown adipose tissues of animals starved for 3 days, biochemical G6Pase activity increased, but hexokinase activity did not change. In white adipose tissues of normal, cold-exposed, or starved animals, G6Pase activity was very low, although the enzyme activity increased slightly in animals starved for 3 days. The results show that the high G6Pase activity in brown adipose cells probably relates to thermogenesis in cold-exposed animals and may be concerned with glucose release into the blood in starved animals.
Anat Rec 1987 Sep
PMID:Significance of increase in glucose 6-phosphatase activity in brown adipose cells of cold-exposed and starved mice. 282 61


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