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)

Affinity of glucose, fructose and mannose for tumour hexokinase and their rates of phosphorylation at saturation concentration have been correlated with rates of glycogen synthesis by intact tumour cells at different concentrations of the three substrates. Competition experiments with one sugar labelled and the other sugar unlabelled indicate inhibition of glycogen synthesis by the sugar with a low K(m) for hexokinase. Glycogen synthesis from glucose 1-phosphate in aged cells and from nucleoside in freshly prepared cells is stimulated by fructose and inhibited by glucose. The decrease in glycogen formation from glucose 1-phosphate by oligomycin is partially overcome by increased fructose concentrations. These results are explained by an activation of alpha-glucan phosphorylase by fructose and an inhibition of this enzyme by glucose. It is suggested that differences in localization of glucose 6-phosphate, available to the intact cell in various ways, determine its transformation into glycogen by either the UDP-glucose-alpha-glucan glucosyltransferase reaction or by the alpha-glucan phosphorylase reaction.
 ...
PMID:Pathways of glycogen synthesis in Novikoff ascites-hepatoma cells. 431 21

The physiological properties of transgenic tobacco plants (Nicotiana tabacum L.) with decreased or increased transport capacities of the chloroplast triose phosphate/phosphate translocator (TPT) were compared in order to investigate the extent to which the TPT controls metabolic fluxes in wild-type tobacco. For this purpose, tobacco lines with an antisense repression of the endogenous TPT (alphaTPT) and tobacco lines overexpressing the TPT gene isolated from the C4 plant Flaveria trinervia (FtTPT) were used. The F. trinervia TPT expressed in yeast cells exhibited transport characteristics identical to the TPT from C3 plants. Neither antisense TPT plants nor FtTPT overexpressors showed a phenotype when grown in a greenhouse in air. Contents of starch and soluble sugars in upper source leaves were similar in TPT underexpressors and FtTPT overexpressors compared to the wild type at the end of the photoperiod. The FtTPT overexpressors incorporated more 14CO2 in sucrose than the wild type, indicating that the TPT limits sucrose biosynthesis in the wild type. There were only small effects on labelling of amino acids and organic acids. The mobilisation of starch was enhanced in alphaTPT lines but decreased in FtTPT overexpressors compared to the wild type. Enzymes involved in starch mobilisation or utilisation, such as alpha-amylase or hexokinase were increased in alphaTPT plants and, in the case of amylases, decreased in FtTPT overexpressors. Moreover, alpha-amylase activity exhibited a pronounced diurnal variation in alphaTPT lines with a maximum activity after 8 h in the light. These changes in starch hydrolytic activities were confirmed by activity staining of native gels. Activities of glucan phosphorylases were unaffected by either a decrease or an increase in TPT activity. There were also effects of TPT activities on steady-state levels of phosphorylated intermediates as well as total amino acids and malate. In air, there was no or little effect of altered TPT transport activity on either rates of photosynthetic electron transport and/or CO2 assimilation. However, in elevated CO2 (1500 microl x l(-1)) and low O2 (2%) the rate of CO2 assimilation was decreased in the alphaTPT lines and was slightly higher in FtTPT lines. This shows that the TPT limits maximum rates of photosynthesis in the wild type.
 ...
PMID:Control of carbon partitioning and photosynthesis by the triose phosphate/phosphate translocator in transgenic tobacco plants (Nicotiana tabacum L.). I. Comparative physiological analysis of tobacco plants with antisense repression and overexpression of the triose phosphate/phosphate translocator. 1075 Aug 94

Glucose metabolism by Prevotella intermedia and Prevotella nigrescens were investigated. Glucose increased the anaerobic growth of these bacteria and promoted the accumulation of intracellular polysaccharide. The polysaccharide was confirmed to be glycogen-like glucan by the absorption spectrum of iodinepolysaccharide complex and the sugar composition. The washed cells consumed glucose anaerobically and converted a part of glucose into the metabolic end-products acetate, formate and succinate. The rest of glucose was confirmed to be accumulated as intracellular polysaccharide. The cells grown in the presence of glucose produced acetate, formate and succinate without exogenous glucose along with the consumption of intracellular polysaccharide. The metabolism of glucose and intracellular polysaccharide required bicarbonate. Prevotella cells had hexokinase and a set of the usual enzymes of the Embden-Meyerhof-Parnas pathway except that phosphofructokinase was pyrophosphate-dependent. A series of enzymes, including phosphoenolpyruvate carboxylase, phosphoenolpyruvate carboxykinase, malate dehydrogenase, fumarase and fumarate reductase, was found for succinate formation. Another series of enzymes, pyruvate oxidoreductase, pyruvate formate-lyase, phosphotransacetylase and acetate kinase was found for acetate and formate formation. Glucose 1,6-bisphosphate-dependent phosphoglucomutase and fructose 1,6-bisphosphate-activated UDP-glucose pyrophosphorylase were detected for glycogen synthesis, while glycogen phosphorylase was for glycogen degradation. The capacity of intracellular polysaccharide formation in addition to glucose fermentation could be advantageous for survival in the supragingival area as well as in the subgingival area.
 ...
PMID:Glucose metabolism by Prevotella intermedia and Prevotella nigrescens. 1115 2

Enzymes were investigated for their occurrence in the cell wall fraction (4,000 g sediment of the homogenate) of Agaricus bisporus sporocarps. Besides the markers malate dehydrogenase (MalDH), hexokinase (HK) and ATPase, the range of entities studied included gamma-glutamyl transferase (gamma-GT), mannitol dehydrogenase (MDH), phenoloxidase, chitin and beta-1,3-glucan synthases (ChS, beta-GS), chitinase, beta-N-acetylhexosaminidase (HexNAc'ase) and beta-glucanase. Using the extractability in dilute buffer, digitonin and NaCl at high ionic strength as the operational criteria, four categories (I-IV) of enzyme-wall associations could be discerned: category I encompasses enzymes which are artefactually present (i.e. contaminants); category II, enzymes that are hydrophobically bound (which may or may not be genuinely wall-associated), III includes enzymes that are ionically bound and IV, enzymes whose bonding to the wall is in all probability covalent. The same enzyme entity may have representatives in more than one category, e.g. ChS and beta-GS (I, II, IV), phenolase (I, II, III, IV), beta-glucanase, chitinase and HexNAc'ase (I, IV). It is thought that the categorization presented could be of general applicability in fungi as well as in higher plants to specify enzyme-wall associations in a straightforward, comparable manner, thus avoiding some of the ambiguous terms prevailing in the literature, such as "weakly", "strongly" or "tightly" wall bound. The results are discussed in more detail for several of the more economically important enzymes studied.
 ...
PMID:A system of categorizing enzyme-cell wall associations in Agaricus bisporus, using operational criteria. 1160 7

1. During development of the sheep, the activities of UDP-glucose-alpha-glucan glucosyltransferase and UDP-glucose pyrophosphorylase and the glycogen content are highest in the liver of lambs 2 weeks old and considerably lower in liver from adult sheep. 2. The activity of hexokinase and the rate of incorporation of [(14)C]-glucose into glycogen are much lower in liver from postnatal sheep than in rat liver. 3. The activities of hexose diphosphatase and glucose 6-phosphatase and the rates of incorporation of [(14)C]pyruvate and [(14)C]propionate into glycogen increase from low levels in the liver of foetal sheep to maxima a few weeks after birth. The activities in the liver of adult sheep are slightly lower. 4. The incorporation rate of [(14)C]pyruvate into glucose has been measured in liver slices from rats, sheep and chick embryos at several ages of these animals. This pathway is active in liver from foetal sheep, embryonic chicks and postnatal rats or sheep, but is absent from the liver from foetal rats. 5. Fructose metabolism, as measured by the rates of incorporation of [(14)C]fructose into glycogen and glucose in liver slices and by assays of liver ketohexokinase, is barely detectable in the liver of foetal sheep and appears soon after birth. 6. During development of the sheep, the incorporation rate of [(14)C]galactose into glycogen in liver slices is highest in foetal sheep and decreases with increasing age of the animal. 7. These findings are discussed with reference to the changing pattern of carbohydrate metabolism during neonatal development of liver in the sheep.
 ...
PMID:CARBOHYDRATE METABOLISM IN LIVER FROM FOETAL AND NEONATAL SHEEP. 1433 56

Promotion of cell wall synthesis (from glucose) in pea (Pisum sativum) stem segments by indoleacetic acid (IAA) develops over a period of 1 to 2 hours and is comprised of a promotion of glucose uptake plus a promotion of the utilization of absorbed glucose. The effect of IAA resembles, in these and other respects, its effect on cell wall synthesis in oat coleoptile segments, but the pea system differs in not being inhibited by galactose or mannose, in involving considerably more isotope dilution by endogenous substrates, and in certain other respects.EFFECTOR INFLUENCES UPON AND TOTAL ACTIVITIES OF THE FOLLOWING ENZYMES OBTAINED FROM ETIOLATED PEA STEM SEGMENTS PRETREATED WITH OR WITHOUT IAA WERE EXAMINED: phosphoglucomutase, uridine diphosphate glucose (UDP-glucose) pyrophosphorylase, nucleoside diphosphokinase, UDP-glucose dehydrogenase, inorganic pyrophosphatase, hexokinase (particulate and soluble), and UDP-glucose-beta-1,4-glucan-glucosyl transferase (beta-glucan synthetase). The first three enzymes mentioned exhibit high activity relative to the flux in vivo, do not appear to show physiologically significant effector responses, and are concluded not to be control points. UDP-glucose dehydrogenase activity is regulated by UDP-xylose. Hexokinase is a potential control point but does not exhibit regulatory effects related to the IAA response. beta-Glucan synthetase is the only one of these enzymes with activity which is increased by treatment of tissue with IAA, and this may be responsible for the effect of IAA on wall synthesis.Assays of metabolite pools support the conclusion that stimulation of polysaccharide synthesis by IAA is due partly to changes in hexokinase reaction rate resulting from an increase in metabolic glucose pool size caused by increased glucose uptake, and partly to increased activity at the polysaccharide synthetase level.
 ...
PMID:Regulation by auxin of carbohydrate metabolism involved in cell wall synthesis by pea stem tissue. 1665 56

Gibberellic acid (GA) stimulated both the elongation of Avena sativa stem segments and increased synthesis of cell wall material. The effects of GA on glucose metabolism, as related to cell wall synthesis, have been investigated in order to find specific events regulated by GA. GA caused a decline in the levels of glucose, glucose 6-phosphate, and fructose 6-phosphate if exogenous sugar was not supplied to the segments, whereas the hormone caused no change in the levels of glucose 6-phosphate, fructose 6-phosphate, UDP-glucose, or the adenylate energy charge if the segments were incubated in 0.1 m glucose. No GA-induced change could be demonstrated in the activities of hexokinase, phosphoglucomutase, UDP-glucose pyrophosphorylase, or polysaccharide synthetases using UDP-glucose, UDP-galactose, UDP-xylose, and UDP-arabinose as substrates. GA stimulated the activity of GDP-glucose-dependent beta-glucan synthetase by 2- to 4-fold over the control. When glucan synthetase was assayed using UDP-glucose as substrate, only beta-1,3-linked glucan was synthesized in vitro, whereas with GDP-glucose, only beta-1,4-linked glucan was synthesized. These results suggest that one part of the mechanism by which GA stimulates cell wall synthesis concurrently with elongation in Avena stem segments may be through a stimulation of cell wall polysaccharide synthetase activity.
 ...
PMID:Regulation of glucose metabolism and cell wall synthesis in Avena stem segments by gibberellic Acid. 1666 May 24

As starch is the main seed reserve material in both species of Araucaria of South America, A. araucana and A. angustifolia, it is important to understand starch breakdown in both embryo and megagametophyte tissues of Araucaria seeds. Sugar analysis by thin layer chromatography indicates that sucrose is the main sugar produced in both tissues. Enzyme reactions coupled to benzidine oxidation indicate that sucrose is the main sugar moved from the megagametophyte to the growing regions of the embryo via the cotyledons.Phosphorylase was detected in both embryo and megagametophyte tissues by the formation of [(32)P]glucose-1-P and by formation of [(14)C] amylopectin from [(14)C]glucose-1-P. The enzyme activity increases 5-fold in both embryo and gametophyte to a peak 18 hours after the start of imbibition. Debranching enzyme, alpha-glucosidase, and hexokinase are also present in both embryonic and megagametophytic tissues.Branched glucan oligosaccharides accumulate during this time, reaching a maximum 40 hours after imbibition starts, and decline after germination occurs.The pattern of activity of the enzymes studied in this work suggests that starch degradation is initiated by alpha-amylase and phosphorylase in the embryo and by phosphorylase mainly in the megagametophyte. Sucrose-P synthase seems to be the enzyme responsible for sucrose synthesis in both tissues.
 ...
PMID:Starch Degradation Metabolism towards Sucrose Synthesis in Germinating Araucaria araucana Seeds. 1666 47