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)

Secondary 18O isotope effects in the gamma-position of ATP have been measured on phosphoryl transfer catalyzed by yeast hexokinase in an effort to deduce the structure of the transition state. The isotope effects were measured by the remote-label method with the exocyclic amino group of adenine as the remote label. With glucose as substrate, the secondary 18O isotope effect per 18O was 0.9987 at pH 8.2 and 0.9965 at pH 5.3, which is below the pK of 6.15 seen in the V/K profile for MgATP. With the slow substrate 1,5-anhydro-D-glucitol, the value was 0.9976 at pH 8.2. While part of the inverse nature of the isotope effect may result from an isotope effect on binding, the more inverse values when catalysis is made more rate limiting by decreasing the pH or switching to a slower substrate suggest a dissociative transition state for phosphoryl transfer, in agreement with predictions from model chemistry. The 18O equilibrium isotope effect for deprotonation of HATP3- is 1.0156, while Mg2+ coordination to ATP4- does not appear to be accompanied by an 18O isotope effect larger than 1.001.
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PMID:Secondary 18O isotope effects for hexokinase-catalyzed phosphoryl transfer from ATP. 201 21

It was verified, by n.m.r. and fast-atom-bombardment-m.s. studies, that the C-2 position of 1,5-anhydro-D-fructose, which was prepared by the reaction of immobilized glucose 2-oxidase from Coriolus versicolor (with 1,5-anhydro-D-glucitol), is hydrated to the acetal form in water. The effects of 1,5-anhydro-D-fructose on several glucose-metabolizing enzymes were compared with those of 1,5-anhydro-D-glucitol. Glucose 1-oxidase from Aspergillus niger was inhibited by 1,5-anhydro-D-fructose (Ki 6.6 mM) more effectively than 1,5-anhydro-D-glucitol (Ki 82.5 mM). Yeast and rat brain hexokinases phosphorylated 1,5-anhydro-D-fructose (Km,yeast 2.3 mM: Km,rat 0.79 mM) and 1,5-anhydro-D-glucitol (Km,yeast 3.9 mM; Km,rat 0.83 mM). The phosphorylated forms of these compounds inhibited D-glucose phosphorylation by yeast hexokinase (Ki of phosphorylated 1,5-anhydro-D-fructose 0.11 mM; Ki of phosphorylated 1,5-anhydro-D-glucitol 0.38 mM) and rat brain hexokinase (Ki of phosphorylated 1,5-anhydro-D-fructose 0.07 mM; Ki of phosphorylated 1,5-anhydro-D-glucitol 0.04 mM). Glucokinase phosphorylated neither 1,5-anhydro-D-fructose nor 1,5-anhydro-D-glucitol, and the phosphorylation of D-glucose by glucokinase was inhibited by them. Mutarotase was slightly inhibited by 1,5-anhydro-D-fructose, as well as by 1,5-anhydro-D-glucitol.
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PMID:Effects of 1,5-anhydro-D-fructose on selected glucose-metabolizing enzymes. 829 6

The aim of the study was to set up a novel fully enzymatic method for screening glucose and 1,5-anhydro-D-glucitol (1,5-AG) in one cuvette. We have determined glucose and 1,5-AG, based on glucokinase (GK) converting glucose to G6P, a compound that can be catalyzed ultimately into 6-PGA by G-6PD and its coenzyme NADP(+), and then calculated glucose concentration according to absorbance variety. Furthermore, pyranose oxidase was used to oxidize 1,5-AG with the formation of 1, 5-anhydro-fructose and H(2)O(2). Measurement was done according to Trinder's reaction principle. The mean within-run and day-to-day precision (CV) of this method for glucose was 0.88% and 1.4%, and also that for 1,5-AG was 1.05% and 1.94%, respectively. The mean recovery rate of two targets was 100.2% and 101.6%, respectively. The correlation (R(2)) between the results of 1,5-AG obtained with our proposed method (y) and those obtained with LanaAG method (x) was 0.999 (y=1.002x-0.675 micromol/l; n=86), and the correlation (R(2)) of glucose between the results obtained with our GK method (y) and those obtained with recommendatory hexokinase method (x) was 0.9999 (y=1.0043x+0.1229 mmol/l; n=86). The reference range (95%) of serological glucose and 1,5-AG was 3.7 to 5.7 mmol/l (4.70+/-0.51 mmol/l) and 83.1 to 240.7 micromol/l (161.9+/-40.2 micromol/l), respectively; and there was no difference with age and sex (P>0.05). This newly developed method was dependable and steady-going, with analysis automatization, and allows quicker and easier measurement of serum glucose and 1,5-AG in one identical reaction cuvette in-phase than previously described methods.
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PMID:A novel fully enzymatic method for determining glucose and 1,5-anhydro-D-glucitol in serum of one cuvette. 1833 75