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)

Acetaminophen, p-aminophenol, and oxyphenbutazone interfere with the glucose oxidase/peroxidase method for glucose. Structurally related compounds that lack a free phenolic hydroxyl group (acetanilide, aniline, and phenylbutazone) do not interfere. During the analytical procedure acetaminophen is consumed. One mole of acetaminophen leads to an apparent loss of four moles of glucose. The hexokinase/glucose-6-phosphate dehydrogenase method (Boehringer Hexokinase method) is not affected by these substances.
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PMID:Interference by acetaminophen in the glucose oxidase-peroxidase method for blood glucose determination. 97 21

A practical biosensor system has been developed for the determination of urinary glucose using a flow-injection analysis (FIA) amperometric detector and ion-exchange chromatography. Glucose oxidase was immobilized onto porous aminopropyl glass beads via glutaraldehyde activation to form an immobilized enzyme column. On the basis of its negative charge at pH 5.5, endogenous urate in urine samples was effectively retained by an upstream anion-exchange resin column. The biosensor system possessed a sensitivity of 160 +/- 2.4 RU microM-1 (RU or relative unit is defined as 2.86 microV at the detection output) for glucose with a minimum detection level of 10 microM. When applied for the determination of urinary glucose, the result obtained compared very well with that of the widely accepted hexokinase assay. The immobilized glucose oxidase could be reused for more than 1000 repeated analyses without losing its original activity. The reuse of the acetate anion-exchange column before replacement would be about 25-30 analyses. Acetaminophen and ascorbic acid were also effectively adsorbed by the acetate anion exchanger. The introduction of this type of anion exchanger thus greatly improved the selectivity of the FIA biosensor system and fostered its applicability for the determination of glucose in urine samples.
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PMID:Determination of urinary glucose by a flow injection analysis amperometric biosensor and ion-exchange chromatography. 130 63

The effect of epinephrine (E) infusion on insulin-mediated glucose metabolism in humans has been studied. Eight glucose-tolerant men were studied on two separate occasions: 1) during 120 min of euglycemic hyperinsulinemia (UH, approximately 5 mM; 40 mU.m-2.min-1); and 2) during UH while E was infused (UHE, 0.05 microgram.kg-1.min-1). Biopsies were taken from the quadriceps femoris muscle before and after each clamp. Glucose disposal, correcting for endogenous glucose production, was 36 +/- 3 and 18 +/- 2 (SE) mumol.kg fat-free mass (FFM)-1.min-1 during the last 40 min of UH and UHE, respectively (P less than 0.001). Nonoxidative glucose disposal (presumably glycogenesis) averaged 23.0 +/- 3.0 and 4.0 +/- 1.1 (P less than 0.001), whereas carbohydrate oxidation (which is proportional to glycolysis) averaged 13.1 +/- 1.4 and 15.3 +/- 1.1 mumol.kg FFM-1.min-1 (P less than 0.05) during UH and UHE, respectively. UHE resulted in significantly higher contents of UDP-glucose, hexose monophosphates, postphosphofructokinase intermediates, and glucose 1,6-bisphosphate (G-1,6-P2) in muscle (P less than 0.05-0.001), but there were no significant differences in high-energy phosphates or fructose 2,6-bisphosphate (F-2,6-P2) between treatments. Fractional activities of phosphorylase increased (P less than 0.01), and glycogen synthase decreased (P less than 0.001) during UHE. It is concluded that E inhibits insulin-mediated glycogenesis because of an inactivation of glycogen synthase and an activation of glycogenolysis. E also appears to inhibit insulin-mediated glucose utilization, at least partly, because of an increase in G-6-phosphate (which inhibits hexokinase) and enhances glycolysis by G-1,6-P2-, fructose 6-phosphate-, and F-1,6-P2-mediated activation of PFK.
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PMID:Epinephrine inhibits insulin-mediated glycogenesis but enhances glycolysis in human skeletal muscle. 190 Jun 69

The effect of bicycle exercise (75% of maximal oxygen uptake) on glucose uptake by the inferior limb (LGU) and glycolysis in human skeletal muscle has been investigated. Biopsies were obtained from the quadriceps femoris muscle before exercise, after 5 and 40 min of exercise, and at fatigue [74.9 +/- 4.7 (SE) min]. LGU was 0.05 +/- 0.02 mmol/min at rest, increased approximately sevenfold after 5 min of exercise, and continued to increase linearly during the first 40 min of exercise. Thereafter LGU stabilized at approximately 1.4 mmol/min until fatigue. Intracellular glucose was low at rest but increased sixfold after 5 min of exercise (P less than 0.01 vs. rest); thereafter, intracellular glucose decreased and was not significantly different from the value at rest after 40 min or at fatigue (P greater than 0.05). D-Glucose 6-phosphate (G-6-P) and alpha-D-glucose 1,6-bisphosphate (G-1,6-P2) (inhibitors of hexokinase) increased significantly after 5 min of exercise (approximately 300% G-6-P; approximately 25% G-1,6-P2) and then decreased continuously. The muscle glycolytic rate (glycogenolysis + glucose uptake) averaged 7.7 mmol.kg dry wt-1.min-1 during the first 40 min of exercise and 3.7 mmol.kg dry wt-1.min-1 during the last 35 min of exercise. The contribution of extracellular glucose to muscle glycolysis was estimated to be only 5 and 19% during the initial and latter phases of exercise, respectively. It is concluded that, during the initial phase of exercise, glucose utilization is limited by phosphorylation, probably due to G-6-P-dependent inhibition of hexokinase.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Regulation of glucose utilization in human skeletal muscle during moderate dynamic exercise. 200 94

Glucose 1,6-bisphosphate (G-1,6-P2) is a potent activator of phosphofructokinase (PFK) and an inhibitor of hexokinase in vitro. It has been suggested that increases in G-1,6-P2 are a main means by which PFK can achieve significant catalytic function in vivo despite falling pH and that increases in G-1,6-P2 will inhibit hexokinase in vivo. The purpose of the present study was to determine whether contraction-induced changes in flux through PFK and hexokinase are associated with changes in G-1,6-P2 in skeletal muscle. Ten men performed bicycle exercise for 10 min at 40 and 75% of maximal O2 uptake (VO2max) and to fatigue [4.8 +/- 0.6 (SE) min] at 100% VO2max. Biopsies were obtained from the quadriceps femoris muscle at rest and after each work load and analyzed for G-1,6-P2. G-1,6-P2 averaged 111 +/- 13 mumol/kg dry wt at rest and 121 +/- 16, 123 +/- 15, and 123 +/- 11 mumol/kg dry wt after the low-, moderate-, and high-intensity exercise bouts, respectively (P less than 0.05 for all means vs. rest). Flux through PFK was estimated to increase exponentially as the exercise intensity increased and muscle pH decreased at the higher work loads, whereas flux through hexokinase was estimated to increase during exercise at 40 and 75% VO2max but decrease sharply at 100% VO2max. These data demonstrate that flux through neither PFK nor hexokinase is mediated by changes in G-1,6-P2 in human skeletal muscle during short-term dynamic exercise.
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PMID:Carbohydrate metabolism in human skeletal muscle during exercise is not regulated by G-1,6-P2. 296 83

The content of glucose 1,6-bisphosphate (G-1,6-P2), an in vitro activator of phosphofructokinase (a rate-limiting enzyme for glycolysis), and the glycolytic rate in skeletal muscle during isometric contraction have been determined. Subjects contracted the knee extensor muscles at two-thirds maximal voluntary force to fatigue. Biopsies from the quadriceps femoris muscle were obtained before and immediately after contraction. G-1,6-P2 increased in all subjects from a mean of 101 +/- 15 (SE) mumol/kg dry wt at rest to 128 +/- 24 at fatigue (P less than 0.05). Muscle glucose did not change significantly, whereas hexosemonophosphates were significantly increased after contraction. The glycogenolytic and glycolytic rate averaged 70.0 +/- 13.8 and 47.3 +/- 6.7 mmol.kg dry wt-1.min-1, respectively, and the glycolytic rate was positively correlated with the accumulation rates of fructose 6-phosphate (F-6-P) (r = 0.95, P less than 0.01) and G-6-P (r = 0.96, P less than 0.01). Phosphocreatine and ATP decreased by 87 and 17%, respectively, whereas ADP increased by 31% after contraction. These data demonstrate that intense, short-term isometric contraction results in an elevation of the muscle content of G-1,6-P2. The increase in G-1,6-P2 could not be accounted for by the side reactions of phosphoglucomutase or phosphofructokinase. It remains to be determined whether the observed increase in G-1,6-P2 is sufficient to account for the high glycolytic rate during intense exercise. The lack of increase in muscle glucose while G-6-P increased (which will inhibit hexokinase) suggests that the debranching enzyme complex was not active during contraction.
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PMID:G-1,6-P2 in human skeletal muscle after isometric contraction. 340 60

The effects of 120 min of euglycaemic hyperinsulinaemia (UH, approximately 5 mM; 40 mU m-2 min-1), UH plus adrenaline infusion (0.05 microgram kg-1 min-1), and hyperglycaemic normoinsulinaemia (26 mM) on hexokinase kinetics in human skeletal muscle were examined. Biopsies were obtained from the quadriceps femoris muscle before and after each clamp. Total muscle hexokinase activity (HKt) (measured on a 2500 g supernatant) at a saturating level of the substrate glucose (1 mM) averaged 13 mmol kg dry wt-1 min-1 in the basal state and did not change significantly under any condition. Soluble hexokinase activity (HKs) (16,000 g supernatant) accounted for approximately 65% of HKt in the basal state, and this percentage was not significantly affected by any condition, suggesting that there was no major transfer of HK between cytosol and mitochondria. The activity of HKt and HKs was inhibited by glucose 1,6-bisphosphate (G-1,6-P2) in a concentration dependent manner in the basal state, and the sensitivity to G1,6-P2 inhibition was not altered by any condition. The activity of HKt and HKs in the presence of a subsaturating level of glucose (0.1 mM) accounted for approximately 70% of the activity at 1 mM glucose, and this percentage was not altered by any condition. These data suggest that under the present conditions alterations in the rates of whole body glucose disposal cannot be associated with alterations in HK distribution between cellular compartments nor its measured kinetics properties.
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PMID:Hexokinase kinetics in human skeletal muscle after hyperinsulinaemia, hyperglycaemia and hyperepinephrinaemia. 797 26

Rabbit tibialis anterior muscles were stimulated continuously at 10 Hz for periods ranging from 2 min to 96 h and were analyzed for energy reserves and metabolic intermediates. Glycogen, ATP and phosphocreatine fell rapidly during the first 5 min of stimulation. Glycogen continued to fall to very low levels, whereas ATP and phosphocreatine rose, reaching 70% of control by 1 h, despite ongoing stimulation. After 2 h, glycogen also increased, regaining control levels in 4 days. Glucose rose to 4.5 times control in 30 min and still exceeded 2.5 times control at 24 h. In the first 2 min, glycolytic intermediates, glucose 6-phosphate (G-6-P), fructose 1,6-bisphosphate, lactate, and pyruvate more than doubled and then returned to control levels or below. Malate and 3-glycerophosphate rose 600 and 200%, respectively. Both of these compounds participate in shuttling reducing equivalents from cytoplasm into mitochondria. Citrate and alpha-ketoglutarate underwent much more modest changes. Glucose 1,6-bisphosphate (G-1,6-P2) fell to one-third of control by 2 h and then rose dramatically at 4 h. At 4 days it was still twice control. The 6-phosphogluconate (6PG) doubled at 2 min, then rose to 12 times control at 2 h, fell somewhat, and peaked at 16 times control at 24 h. Aspartate and alanine both exhibited a biphasic rise in concentration, whereas glutamate fell to 30% in 15 min and rose slowly after 4 h. The rise in glucose was interpreted to be the consequence of rapid glycogenolysis together with inhibition of hexokinase by G-1,6-P2 and elevated G-6-P. Paradoxically, glycogen resynthesis apparently occurred when the glycogen synthase stimulator, G-6-P, was very low, and the glycolysis stimulator, G-1,6-P2, was high. Although G-1,6-P2 is an inhibitor of 6PG dehydrogenase, the timing of the changes in G-1,6-P2 and 6PG levels suggests that the accumulation of 6PG was initiated by some other influence.
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PMID:Changes in ATP, phosphocreatine, and 16 metabolites in muscle stimulated for up to 96 hours. 889 22

All of the 2,6-dideoxy sugars contained within the structure of chromomycin A3 are derived from D-glucose. Enzyme assays were used to confirm the presence of hexokinase, phosphoglucomutase, UDPG pyrophosphorylase (UDPGP), and UDPG oxidoreductase (UDPGO), all of which are involved in the pathway of glucose activation and conversion into 2,6-dideoxyhexoses during chromomycin biosynthesis. Levels of the four enzymes in Streptomyces spp. cell extracts were correlated with the production of chromomycins. The pathway of sugar activation in Streptomyces spp. involves glucose 6-phosphorylation by hexokinase, isomerization to G-1-P catalyzed by phosphoglucomutase, synthesis of UDPG catalyzed by UDPGP, and formation of UDP-4-keto-6-deoxyglucose by UDPGO.
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PMID:Enzymatic conversion of glucose to UDP-4-keto-6-deoxyglucose in Streptomyces spp. 975 28