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)

Isolated ovine adipocytes were incubated in vitro with specifically labeled 14C-glucose in the presence or absence of acetate. The flux patterns of glucose carbon through major metabolic pathways were estimated. When glucose was added as the sole substrate, approximately equal portions of glucose carbon (10%) were oxidized to CO2 in the pentose phosphate pathway, in the pyruvate dehydrogenase reaction and in the citrate cycle. Fifteen percent of the glucose carbon was incorporated into fatty acids and 43% was released as lactate and pyruvate. Addition of acetate to the medium increased glucose carbon uptake by 1.5-fold. Most of this increase was accounted for by a sevenfold increase in the activity of the pentose phosphate pathway. Acetate increased glucose carbon fluxes via pentose phosphate pathway to triose phosphates, from triose phosphate to pyruvate, into glyceride glycerol, into lactate and pyruvate and into pyruvate dehydrogenase and citrate cycle CO2. Glucose carbon incorporated into fatty acids was decreased 50% by acetate while, carbon fluxes through the phosphofructokinase-aldolase reactions were not significantly increased. Results of this study suggest that, when glucose is the sole substrate, the conversion of glucose to fatty acids in ovine adipocytes may not be limited by the maximum capacity of hexokinase, the pentose phosphate pathway or enzymes involved in the conversion of triose phosphates to pyruvate and of pyruvate to fatty acid. Acetate increased glucose utilization apparently by increasing activity of the pentose phosphate pathway as a result of enhanced NADPH utilization for fatty acid synthesis.
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PMID:Glucose metabolism and effect of acetate in ovine adipocytes. 714 48

1. The following were measured in adipose-tissue pieces, obtained from 7-9 month-old sheep, before or after the tissue pieces had been maintained in tissue culture for 24 h: the rates of synthesis from glucose of fatty acids, acylglycerol glycerol, pyruvate and lactate; the rate of glucose oxidation to CO(2); the rate of glucose oxidation via the pentose phosphate pathway; the activities of hexokinase, glucose 6-phosphate dehydrogenase, phosphofructokinase, pyruvate kinase, pyruvate dehydrogenase and ATP citrate lyase; the intra- and extra-cellular water content; the concentration of various metabolites and ATP, ADP and AMP. 2. The proportion of glucose carbon converted into the various products in sheep adipose tissue differs markedly from that observed in rat adipose tissue. 3. There was a general increase in the rate of glucose utilization by the adipose-tissue pieces after maintenance in tissue culture; largest changes were seen in the rates of glycolysis and fatty acid synthesis from glucose. These increases are paralleled by an increase in pyruvate kinase activity. There was no change in the activities of the other enzymes as measured, although the net flux through all the enzymes increased. 4. Incubation of fresh adipose-tissue pieces for 2-6h led to an increase in the affinity of pyruvate kinase for phosphoenolpyruvate. 5. The rate of pyruvate production by glycolysis was greater than the activity of pyruvate dehydrogenase of the tissue. 6. The results suggest that both pyruvate kinase and pyruvate dehydrogenase have important roles in restricting the utilization of glucose carbon for fatty acid synthesis in sheep adipose tissue.
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PMID:Regulation of glycolysis and fatty acid synthesis from glucose in sheep adipose tissue. 715 Feb 63

The activities (per g of tissue) of hexokinase, phosphofructokinase and pyruvate kinase were unchanged throughout lactation in liver and in kidney cortex. In both these tissues glucose 6-phosphatase activity decreased during late lactation. At the same time fructose diphosphatase activity increased in kidney cortex but not in liver. Activities of the pentose cycle dehydrogenases and of aspartate aminotransferase tended to increase in mid lactation. For most enzymes the activities at peak lactation were similar to those for dry, non-pregnant cows and there was no specific response of the gluconeogenic enzymes. Total hepatic contents of most enzymes tended to increase in mid lactation, but the changes were not clear cut and were the result of an increase in liver size.
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PMID:Activities of some enzymes of glucose metabolism in bovine liver and kidney cortex at three stages of lactation. 715 8

A microassay method sensitive enough to analyze the enzyme activities in one oocyte was developed using enzymatic cycling for amplifying the reaction product to 10,000 fold. An oil-well technique was applied in the assay for achieving the reaction in the medium as small as 1.0 to 5.0 microliter. Immature Wistar rats were superovulated by PMS-hCG administration. Oocytes were collected by the puncture of the follicle and the flushing of the tube. They were freeze-dried after washing to remove cumulus cells. The dry weight was about 50ng on a quartz fiber fishpole balance. The activity of hexokinase was 1.75 +/- 0.14 picomol/oocyte/hr corresponding to one-tenth of the ovarian homogenate as control, indicating low capacity of glucose utilization in the oocyte. The activities of G6PD, LDH, and MDH were 8.41 +/- 0.34, 35.7 +/- 2.89. 11.1 +/- 2.5 picomol/oocyte/min, respectively. High activity of G6PD suggests the pentose phosphate shunt concerned with steroidogenesis is active in the oocyte. HCG increased the activities of hexokinase and MDH and decreased that of G6PD. The activity of LDH remained unchanged.
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PMID:[Study of energy metabolism in the oocyte by cycling method]. 717 80

Progesterone decreases the oxidation of 2-deoxyglucose and glucose through the pentose-phosphate pathway in isolated female rat adipocytes and, therefore, the effect of this steroid incubation in vitro, progesterone decreased total hexokinase activity but did not affect the isoenzyme-I activity. Progesterone had no direct effect on fat cell cytosol hexokinase and its action on glucose oxidation was not affected by variations in the concentration of Mg2+, the cofactor of hexokinase. Our data suggest that the decreased activity of hexokinase in the presence of progesterone is due to a decrease in the activity of the insulin-sensitive isoenzyme-II. This results from the steroid acting at a step beyond enzyme activation and may be mediated by a feedback mechanism.
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PMID:Progesterone and glucose metabolism in the female rat adipocyte: effect on hexokinase activity. 717 24

Measurements have been made of the activity of the enzymes of the glycolytic, pentose phosphate and lipogenic pathways and of some marker enzymes of the tricarboxylic acid cycle in brains of rats aged between 20 days and 24 months. In general, the activity of the most enzymes measured was unchanged by aging but exceptions to this were increases of hexokinase, glucose-6-phosphate dehydrogenase and 'malic enzyme' and decreases of ATP-citrate lyase, acetyl-CoA carboxylase and fatty acid synthetase. An exceptionally large (2-fold) increase in the activity of cytosolic glycerol 3-phosphate dehydrogenase was noted. These changes are considered in relation to the overall metabolic activity of the brain.
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PMID:Age-related changes in enzymes of rat brain. 1. Enzymes of glycolysis, the pentose phosphate pathway and lipogenesis. 723 73

The influence of fructose feeding for 1 to 12 days on the activity of enzymes of glycolysis and gluconeogenesis was studied in the jejunal mucosa and the liver of rats. In the jejunal mucosa fructose feeding leads to an increase in the activity of 6-phosphofructokinase (p less than 0.05) and fructose-1.6-bisphosphate aldolase (p less than 0.05), while the activity of hexokinase and glucose-6-phosphate dehydrogenase remains unchanged. Fructose feeding increases the activity of fructose-bisphosphatase in the jejunal mucosa, however, the absolute values of this enzyme remain low (less than 10%) when compared to those in the liver. In the liver fructose feeding is followed by a marked increase of the activity of fructose-bisphosphatase and glucose-6-phosphate dehydrogenase. In contrast, the activity of glucose-6-phosphatase decreases significantly under a fructose enriched diet. The enzyme activity rose to a maximum within 3 days; in the following time of observation no major changes occurred. The results are in accordance with the assumption that fructose feeding leads in the jejunal mucosa mainly to adaptive alterations of the activity of those enzymes which are involved in the breaking-down of fructose, whereas in the liver the activity of those enzymes is increased, which take part in the new synthesis of glucose-6-phosphate or which direct glucose-6-phosphate into the pentose-phosphate.
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PMID:Effect of fructose feeding on the activity of enzymes of glycolysis, gluconeogenesis, and the pentose phosphate shunt in the liver and jejunal mucosa of rats. 727 91

Mouse renal cell tumors (RCTs) were induced in male CBA mice by 5 subcutaneous injections of 8 mg 1,2-dimethylhydrazine (DMH)/kg body weight once a week. After a lag period of 2 yr kidneys were removed, and serial cryostat sections of the kidneys were histochemically analyzed for the following parameters: glycogen content, basophilia, and the activities of glycogen synthase (SYN), glycogen phosphorylase (PHO), glucose-6-phosphatase (G6Pase), glucose-6-phosphate dehydrogenase (G6PDH), hexokinase (HK), pyruvate kinase (PK), lactate dehydrogenase (LDH), malic enzyme (ME), succinate dehydrogenase (SDH), alkaline phosphatase (ALPase) and gamma-glutamyltranspeptidase (GGT). RCTs displayed the same histochemical profile irrespective of their size and growth pattern. In comparison with the normal kidney epithelium, the neoplastic cells exhibited elevated activities of enzymes for glycolysis (HK, PK, LDH) and the pentose phosphate pathway (G6PDH), while negative G6Pase and low SDH activity were observed in these cells. The majority of RCTs showed high PHO activity and weak staining for SYN. Activities of ALPase and GGT were negative in most of the RCTs. Markedly enlarged cells with atypical nuclei were detected in some advanced RCTs. Higher activities of glycolytic and mitochondrial enzymes and G6PDH were found in these enlarged cells than in other tumor cells. Tubular preneoplastic lesions were similar to neoplastic lesions in morphological and histochemical characteristics. The present study revealed that a markedly elevated capacity for glycolysis and the pentose phosphate pathway occurred in RCTs in mice. A similar histochemical pattern in the few preneoplastic tubular lesions observed suggests that these metabolic aberrations emerge early during carcinogenesis, but additional studies on early stages of renal carcinogenesis are needed to substantiate this assumption.
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PMID:Enzymic pattern of preneoplastic and neoplastic lesions induced in the kidney of CBA mice by 1,2-dimethylhydrazine. 781 30

The objective of the present work was to identify the regulatory step(s) in the post-natal development of a high glycolytic capacity previously evidenced in newborn pig enterocytes (Darcy-Vrillon et al. (1994) Pediat. Res., 36, 175-181. Glucose entry via the Na+/glucose cotransporter, estimated by the uptake of the non-metabolizable analogue methyl alpha-D-[U-14C]glucopyranoside, slightly decreased between birth and 2 days of sucking. The flux of glucose metabolized into the pentose cycle pathway slightly increased but could not account for the 3-fold increase observed in the glycolytic capacity. Whereas the maximal activity of 6-phosphofructo-1-kinase did not change between stages, there was a significant increase in hexokinase activity as well as in the flux of glucose phosphorylated. These findings suggest that the stimulation of glucose phosphorylation through hexokinase is the key event leading to an increased glycolytic capacity of small intestinal cells at the onset of sucking.
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PMID:Control of glucose metabolism in newborn pig enterocytes: evidence for the role of hexokinase. 798 Dec 35

31P NMR studies were carried out on the parental drug-sensitive human T-lymphoblastoid cell line CCRI-CEM (CEM) and its multi-drug-resistant (MDR) CEM-VBL100 variants, to assess the role of the pentose phosphate (PP) in MDR expression. CEM and CEM-VBL100 were incubated in the presence of 2-deoxyglucose, as recently proposed by our group (Clin. Chim. Acta 208: 39, 1992). Accumulation of 2-deoxyglucose 6-phosphate was much lower in the drug-resistant than in sensitive cells, indicating PP shunt activation in the MDR variants. This result was confirmed by enzymatic analyses, which demonstrated that, with respect to the parental line, the MDR variant was characterized by a) unaltered hexokinase activity; b) higher glucose 6-phosphate dehydrogenase activity; c) increased levels of reduced glutathione and marked increase of glutathione peroxidase activity after cell exposure to an oxidizing agent (tert-butylhydroperoxide). These results support the view that cell detoxification mechanisms mediated by the pentose phosphate pathway may contribute to the expression of MDR in tumours.
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PMID:Pentose phosphate pathway alterations in multi-drug resistant leukemic T-cells: 31P NMR and enzymatic studies. 810 18


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