Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.1.1 (hexokinase)
 5,274 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The molar absorptivity of NADH at 340 nm has been determined by an indirect procedure in which high-purity glucose is phosphorylated by ATP in the presence of hexokinase, coupled to oxidation of the glucose-6-phosphate by NAD+ in the presence of glucose-6-phosphate dehydrogenase. The average value from 85 independent determinations is 6317 liter mol-1 cm-1 at 25 degrees C and pH 7.8. The overall uncertainty is -4.0 to +5.5 ppt (6292 to 6352 liter mol-1 cm-1), based on a standard error of the mean of 0.48 ppt and an estimate of systematic error of -2.6 to +4.1 ppt. Effects of pH, buffer, and temperature on the molar absorptivity are also reported.
 ...
PMID:Determination of the molar absorptivity of NADH. 0 88

I have re-examined optimum reaction conditions for measurement of creatine kinase (EC 2.7.3.2). The optimum pH is 6.45, and 2,2-bis(hydroxymethyl)-2,2',2''-nitrotriethanol acetate, 200 mmol/liter, is the buffer of choice. Thioglycerol, 20 mmol/liter, is superior for both in-assay reactivation and for storage stability of sera. Fluoride, 25 mmol/liter, a broad inactivator of adenylate kinase (EC 2.7.4.3), has little effect on creatine kinase and is superior to AMP for adenylate kinase inhibition in the assay of creatine kinase. Magnesium ion, ADP, and buffer concentrations are interdependent and their optima must be determined together. The hexokinase/glucose-6-phosphate dehydrogenase activity ratio should not exceed 1.6. The range of linearity is limited by the glucose-6-phosphate dehydrogenase and NAD+ concentrations. Glucose-6-phosphate dehydrogenase, ADP, and NAD+ are the constituents most likely to result in unacceptable blanks. Creatine kinase is inhibited noncompetitively by anions: acetate and fluoride inhibit slightly, but sulfates, nitrates, and excessive chlorides should be avoided.
 ...
PMID:Creatine kinase: re-examination of optimum reaction conditions. 1 66

Effects of glucose concentration and anoxia upon the metabolite concentrations and rates of glycolysis and respiration have been investigated in the perfused liver of the fetal guinea pig. In most cases the metabolite concentrations in the perfused liver were similar to those observed in vivo. Between 50 days and term there was a fall in the respiratory rate and in the concentration of ATP and fructose 1,6-diphosphate and an increase in the concentration of glutamate, glycogen and glucose. Reducing the medium glucose concentration from 10 mM to 1 mM or 0.1 mM depressed lactate production and the concentration of most of the phosphorylated intermediates (except 6-phosphogluconate) in the liver of the 50-day fetus. This indicates a fall in glycolytic rate which is not in accord with the known kinetic properties of hexokinase in the fetal liver. Anoxia increased lactate production by, and the concentrations of, the hexose phosphates ADP and AMP in the 50-day to term fetal liver, while the concentration of ribulose 5-phosphate, ATP and some triose phosphates fell. These results are consistent with an activation of glycolysis, particularly at phosphofructokinase and of a reduction in pentose phosphate pathway activity, particularly at 6-phosphogluconate dehydrogenase. The calculated cytosolic NAD+/NADH ratio for the perfused liver was similar to that measured in vivo and evidence is presented to suggest that the dihydroxyacetone phosphate/glycerol 3-phosphate ratio gives a better indication of cytosolic redox than the lactate/pyruvate ratio. The present observations indicate that phosphofructokinase hexokinase and possibly pyruvate kinase control the glycolytic rate and that glyceraldehyde-3-phosphate dehydrogenase is at equilibrium in the perfused liver of the fetal guinea pig.
 ...
PMID:Some effects of glucose concentration and anoxia on glycolysis and metabolite concentrations in the perfused liver of fetal guinea pig. 2 74

The enzymes mannitol-1-phosphate dehydrogenase, mannitol-1-phosphatase, mannitol dehydrogenase and hexokinase participate in an enzymatic cycle in the fungus Alternaria alternata. One turn of the cycle gives the net result: NADH + NADP+ + ATP leads to NAD+ + NADPH + ADP + Pi. The cycle alone can meet the total need of NADPH formation for fat synthesis in the organism. A polyketide producing strain of A. alternata shows a lower mannitol oxidation as well as a lower fat synthesis than a nonproducing mutant, supporting the hypothesis that polyketide formation is favoured at limiting NADPH production. It is further suggested that the mannitol cycle is regulating the glycolytic flux by substrate withdrawal from phosphofructokinase.
 ...
PMID:Production of NADPH in the mannitol cycle and its relation to polyketide formation in Alternaria alternata. 2 47

The author reports a modification of the UV method UltraZyme Plus alpha-Amyl Harleco and the adaptation to the Eppendorf Enzymautomat 5010. alpha-amylase acts on an oligosaccharide mixture yielding maltose, which is hydrolysed by alpha-glucosidase. The liberated glucose is determined specifically by the hexokinase/glucose-6-phosphate dehydrogenase (NAD+-dependent) method+ by addition of pyruvate, lactate dehydrogenase and ATP. Thereafter the lactate dehydrogenase reaction is stopped by addition of oxamate and the alpha-amylase activity is measured.
 ...
PMID:[Kinetic determination of alpha-amylase in serum and urine with an oligosaccharide as substrate--modification for a fully mechanized enzyme measuring device (author's transl)]. 9 28

1. Cataract formation in streptozotocin-induced diabetes in rats was reduced by approximately 85% when a diet rich in maize oil (300 g/kg diet) (fat diet) was given, thus confirming results of earlier studies. However, the concentration of sorbitol in the lens of diabetic animals remained high, the values for diabetic rats given the standard diet and the fat died being 65 and 40 mumol/g protein respectively. 2. With the standard diet, the fatty acid profile of the triglycerides of the epididymal fat pads was characterized by a greater relative proportion of saturated fatty acids for the diabetic animals compared to that for the normal animals. The fat diet moderated the tendency towards saturation in the diabetic animals. 3. The fat diet had other effects on the diabetic animals; these included a reduced mortality rate, increased body-weight, a decrease in the daily water intake, and in the daily urinary excretion of glucose and urea. 4. In the diabetic animals the fat diet had no effect on the specific activities in the liver of hexokinase (EC 2.7.1.1), glucokinase (EC 2.7.1.2), phosphofructokinase (EC 2.7.1.11) and pyruvate kinase (EC 2.7.1.40). However, the specific activity of glucose-6-phosphatase (EC 3.1.3.9) was reduced, while that of malate dehydrogenase (decarboxylating) (NADP) (EC 1.1.1.40) was increased. The NAD+:NADH ratio, as calculated from liver pyruvate and lactate concentrations, tended to increase. 5. The results suggested that the fat diet moderated the long-term metabolic effects of diabetes.
 ...
PMID:The effect of an unsaturated-fat diet on cataract formation in streptozotocin-induced diabetic rats. 13 11

Development of cirrhosis of liver tissue did not influence the intensity of glycolysis, with glucose as a substrate, in supernatant fraction of liver homogenate in chronic intoxication with CCL4. In preparations of cirrhotic liver, as compared with liver from the intact animals, more distinct activation of glycolysis was caused by addition of ATP and NAD at the stage of 3-week intoxication and also by addition of hexokinase, glyceraldehydephosphate dehydrogenase and lactate dehydrogenase at the stage of distinct cirrhosis of liver (6 weeks of CCL4 intoxication). Km values for glucose-6-phosphate dehydrogenase increased over all the periods of intoxication.
 ...
PMID:[Change in the glycolytic and glucose-6-phosphate dehydrogenase activity in experimental cirrhosis of the liver]. 16 85

The growth of Brucella abortus (US-19) in a complex tryptose-yeast extract medium containing D-glucose is inhibited by 10 mM erythritol. The enzymes of the erythritol pathway, except for D-erythrulose 1-phosphate dehydrogenase (D-glycero-2-tetrulose 1-phosphate:nicotinamide adenine dinucleotide (NAD+) 4-oxidoreductase) were detected in the soluble and membrane fractions of cell extracts. Glucose catabolism by cell extracts was inhibited by erythritol, whereas, phosphorylated intermediates of the hexose monophosphate pathway were converted to pyruvic acid with oxygen consumption. Erythritol kinase (EC 2.7.1.27; adenosine 5'-triphosphate (ATP): erythritol 1-phosphotransferase) was found to be eightfold higher in activity than the hexokinase in cell extracts. In vivo, ATP is apparently consumed with the accumulation of D-erythrulose 1-phosphate (D-glycero-2-tetrulose 1-phosphate) and no substrate level phosphorylation. ATP levels dropped 10-fold in 30 min after addition of erythritol to log phase cells in tryptose-yeast extract medium with D-glucose as the carbon source. These data suggest bacteriostasis in the presence of erythritol results from the ATP drain caused by erythritol kinase.
 ...
PMID:Inhibition of growth by erythritol catabolism in Brucella abortus. 17 Feb 49

The mechanism by which fatty acid addition leads to the inactivation of pyruvate dehydrogenase in intact rat liver mitochondria was investigated. In all cases the fatty acid octanoate was added to mitochondria oxidizing succinate. Addition of fatty acid caused an inactivation of pyruvate dehydrogenase in mitochondria incubated under State 3 conditions (glucose plus hexokinase), in uncoupled, oligomycin-treated mitochondria, and in rotenone-menadione-treated mitochondria, but not in uncoupled mitochondria or in mitochondria incubated under State 4 conditions. A number of metabolic conditions were found in which pyruvate dehydrogenase was inactivated concomitant with an elevation in the ATP/ADP ratio. This is consistent with the inverse relationship between the ATP/ADP ratio and the pyruvate dehydrogenase activity proposed by various laboratories. However, in several other metabolic conditions pyruvate dehydrogenase was inactivated while the ATP/ADP ratio either was unchanged or even decreased. This observation implies that there are likely other regulatory factors involved in the fatty acid-mediated inactivation of pyruvate dehydrogenase. Incubation conditions in State 3 were found in which the ATP/ADP and the acetyl-CoA/CoASH ratios remained constant and the pyruvate dehydrogenase activity was correlated inversely with the NADH/NAD+ ratio. Other State 3 conditions were found in which the ATP/ADP and the NADH/NAD+ ratios remained constant while the pyruvate dehydrogenase activity was correlated inversely with the acetyl-CoA/CoASH ratio. Further evidence supporting these experiments with intact mitochondria was the observation that the pyruvate dehydrogenase kinase activity of a mitochondrial extract was stimulated strongly by acetyl-CoA and was inhibited by NAD+ and CoASH. In contrast to acetyl-CoA, octanoyl-CoA inhibited the kinase activity. These results indicate that the inactivation of pyruvate dehydrogenase by fatty acid in isolated rat liver mitochondria may be mediated through effects of the NADH/NAD+ ratio and the acetyl-CoA/CoASH ratio on the interconversion of the active and inactive forms of the enzyme complex catalyzed by pyruvate dehydrogenase kinase and pyruvate dehydrogenase phosphatase.
 ...
PMID:Regulation of pyruvate dehydrogenase by fatty acid in isolated rat liver mitochondria. 17 49

The investigations carried out have shown that not only AMP but ADP also undergoes direct deamination in both soluble and mitochondrial fractions of rat brain tissue. Deamination of AMP is stimulated by the addition of ATP and the activity of one of the isoenzymes of AMP-aminohydrolase is markedly enhanced by both yeast and brain hexokinase. Activation by hexokinase is mainly due to its SH groups, through which hexokinase reacts with AMP-aminohydrolase, forming, probably, a protein-protein complex in which AMP aminohydrolase activity is considerably increased. Hexokinase does not affect the deamination of ADP and NAD. Further experiments are needed to find out whether the activation of AMP-aminohydrolase is accomplished by hexokinase itself or by an other protein contaminating it. Deamination of NAD, in contrast to AMP and ADP, takes place only in mitochondria and does not occur in the soluble fraction. In mitochondria besides deamination, AMP and ADP undergo intensive dephosphorylation, while the deamination of NAD is not accompanied by an increase of phosphate, i. e. mitochondria lack enzymes which breakdown NAD to mono nucleotides. Our data indicate that the formation of deamino -NAD from NAD and reamination of deamino-NAD by aspartate to NAD by the formation of intermediary NAD-succinate is of greater importance. The formation of the latter and that of deamino-NAD from NAD as well as the presence of preformed deamino-NAD in mitochondria have been demonstrated by Movsessian. The occurrence of these processes in mitochondria and their role in the formation of ammonia from amino acids is of importance in as much as oxaloacetate formation and its conversion to aspartate, which is necessary for the reamination of deamino-NAD, are localized in mitochondria. The main source of the amino nitrogen of aspartate is known to be glutamate, which incorporates the amino nitrogen of most amino acids. alpha-Keto-glutarate, which is necessary for the synthesis of glutamate, is also formed in mitochondria are the most favourable site for the formation of ammonia from amino acids with the participation of pyridine nucleotides. Of the purine mono and dinucleotides studied deamino-NAD is most effective in the formation of ammonia from amino acids in mitochondria since in contrast to purine mono nucleotides, deamino-NAD and NAD are not dephosphorylated in mitochondria. According to some authors the reamination of IMP by aspartate is of importance in the formation of ammonia from amino acids in brain tissue. In our studies, however, IMP was not effective in the formation of ammonia from aspartate in mitochondrial fractions. IDP was found to be more effective. IMP and IDP may probably participate in the formation of ammonia in the soluble fraction, where nucleotidase activity is considerably low.
 ...
PMID:[Role of adenine mono- and dinucleotides in ammonia formation in brain tissue]. 18 42


1 2 3 4 5 6 7 8 9 10 Next >>