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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)

The activity of key glycolysis enzymes (hexokinase, glucose-6-phosphatase, phosphofructokinase, fructose-diphosphatase and ketose-1-phosphate aldolase) in the kidney tissue and its subcellular structures was studied in normal rats and in rats with experimental acute renal insufficiency. It is established that considerable biochemical changes in the kidney tissues affecting all the elements of cellular structures occur under acute lesion of the kidneys. The activity of the enzymes under study under acute renal insufficiency lowers to a greater extent in those subcellular structures of the kidneys where they are mainly localized. The arising disturbances in permeability of the kidneys cellular membranes intensify the release of the mentioned enzymes to blood serum and urine, that in its turn disturbs the coordination of certain glycolysis stages.
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PMID:[Activity of glycolysis key enzymes in subcellular structures of normal kidneys and under acute renal insufficiency]. 22 62

We report the synthesis of adenosine [gamma-(S)-16O,17O,18O]triphosphate, an isotopically labeled species of ATP that is chiral at the gamma-phosphoryl group, the configuration of which has been confirmed by independent stereochemical analysis. This molecule has been used as a substrate in the reactions catalyzed by glycerol kinase and by acetate kinase. The resulting samples of isotopically labeled sn-glycerol 3-phosphate and of acetyl phosphate have been used as substrates in the alkaline phosphatase mediated transfer of the chiral phosphoryl groups to (S)-propane-1,2-diol, whence the configuration at phosphorus has been determined [Abbott, S. J., Jones, S. R., Weinman, S. A., & Knowles, J. R. (1978) J. Am. Chem. Soc. 100, 2558]. It is shown that glycerol kinase and acetate kinase (and, by virtue of an earlier correlation, pyruvate kinase and hexokinase) proceed by pathways that result in inversion of the configuration at phosphorus. The sterochemical approach provides an access to the otherwise cryptic events that are involved in phosphoryl-group transfer within the ternary complexes of these kinases and their substrates.
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PMID:Stereochemical course of phosphokinases. The use of adenosine [gamma-(S)-16O,17O,18O]triphosphate and the mechanistic consequences for the reactions catalyzed by glycerol kinase, hexokinase, pyruvate kinase, and acetate kinase. 22 19

This paper starts a series on red blood cell (RBC) metabolism in patients with chronic renal failure (CRF). The glycolytic enzyme levels and in vitro half-lives of these patients' RBCs were determined. A number of enzymes (hexokinase, glucose-6-phosphate isomerase, fructose-6-phosphate kinase, aldolase, glyceraldehyde-3-phosphate dehydrogenase and lactate dehydrogenase) showed higher activities than in normal control RBCs. Other enzyme activities were normal. These results were discussed and several possible mechanisms considered. We favour the point of view of a shortened life span of the RBCs in CRF, making the most unstable enzymes of the glycolytic sequence appear increase as compared with normal controls.
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PMID:Metabolism of red blood cells in chronic renal failure. I. Glycolytic enzyme levels. 22 98

A protein phosphokinase (EC 2.7.1.1.37) was isolated from baker's yeast (Saccharomyces cerevisiae) after a 17,000-fold purification; the purified enzyme is homogeneous according to the criteria of gel electrophoresis and ultracentrifuge analysis. The enzyme has a high isoelectric point of ca. 9 and appears to exist as a monomer with a molecular weight of 42,000 plus or minus 1500. It is neither stimulated by cyclic 3',5'-AMP, -GMP, -CMP or -ump nor inhibited by the regulatory subunit of rabbit muscle protein kinase (Reimann, E. M., Walsh, D. A., and Krebs, E. G. (1971), J. Biol. Chem. 246, 1986). In the presence of divalent metal ions, preferably Mg-2+ or Mn-2+, the enzyme readily transfers the terminal phosphate group of ATP to phosvitin, alphaS1B- and beta a-casein and an NH2-terminal tryptic peptide derived from beta a-casein, but not to protamine, lysine, or arginine-rich histones or to yeast enzymes such as phosphorylase, phosphofructokinase, or pyruvate carboxylase; serine and polyserine were also inactive as phosphate acceptors. Km values of 0.17 mM for beta a-casein and 0.2 mMfor ATP were determined at 10 mM Mg-2+. The urified yeast protein kinase also catalyzes the reverse reaction, namely, the transfer of phosphate from fully phosphorylated beta a-casein or its NH2-terminal peptide to ADP resulting in the formation of ATP. AMP, GDP, UDP, and CDP did not serve as phosphate acceptors in this reaction. As observed by Rabinowitz and Lipmann (Rabinowitz, M., and Lipmann, F. (1960), J. Biol. Chem. 235, 1043) both reactions have different pHoptima with values of 7.5 for the forward reaction (phosphorylation of the proteins) and ca 5.2 for the formation of ATP; both are differently affected by salts. Phosphorylation of beta a-casein with [gamma-32-P]ATP followed by digestion of the labeled protein with trypsin indicated that all the radioactivity was exclusively introduced in an NH2-terminal peptide possessing the unique sequence: Glu-Ser(P)-Leu-Ser(P)-Ser(P)-Ser(P)-Glu-Glu...(Ribadeau-Dumas, B., Brignon, G., Grosclaude, F., and Mercier, J.-C. (1971), eur J. Biochem. 20, 264). By subjecting beta a-casein and its NH2-terminal peptide to the combined action of almond acid phosphatease and purified yeast protein kinase, it was determined that the phosphorylation and dephosphorylation reactions proceed randomly, i.e., all seryl phosphate residues are equally susceptible and that the rate of phosphorylation decreases drastically as the number of bound phosphate groups in the substrate diminishes.
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PMID:Purification and properties of a yeast protein kinase. 23 75

Using small-angle X-ray scattering from solutions of yeast hexokinase, we have measured the radii of gyration of the monomeric B isozyme and its complexes with sugar substrates. We find that the radius of gyration decreases by 0.95 +/- 0.24 A upon binding glucose and 1.25 +/- 0.28 A upon binding glucose 6-phosphate. This observed reduction in radius of gyration in the presence of glucose is the same as that calculated from the coordinates of the high-resolution crystal structures of native hexokinase B and a glucose complex with hexokinase A. Thus, these measurements suggest that the dramatic closing of the slit between the two lobes of hexokinase observed in the crystal structures (Bennett, W.S., & Steitz, T.A. (1978) Proc. Natl. Acad. Sci. U.S.A. 75, 4848--4852) occurs in solution when either glucose or glucose 6-phosphate is bound.
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PMID:Yeast hexokinase in solution exhibits a large conformational change upon binding glucose or glucose 6-phosphate. 36 1

The inactivation of yeast hexokinase A (ATP:D-hexose 6-phosphotransferase, EC 2.7.1.1) by phenylglyoxal obeys pseudo first-order kinetics. Formation of a reversible enzyme-reagent complex prior to modification is suggested by the observed saturation kinetics. Loss of activity correlates with the incorporation of 1 mol of [14C]phenylglyoxal per mol 50 000 dalton subunit. No significant conformational change occurs concomitantly. Inactivation is attributable to modification of an arginyl residue. The pattern of protection by substrates and analogs favors an interaction of this essential residue with the terminal phosphoryl group of ATP or glucose 6-phosphate.
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PMID:An essential arginyl residue in yeast hexokinase. 36 11

The Raleigh, North Carolina, population of Drosophila melanogaster was examined for linkage disequilibrium in 1974, several years after previous analyses in 1968, 1969, and 1970. alphaglycerol-3-phosphate dehydrogenase-1 (alphaGpdh-1), malate dehydrogenase-1 (Mdh-1), alcohol dehydrogenase (Adh), and hexokinase-C (Hex-C, tentative name, F. M. Johnson, unpublished; position determined by the present authors to be 2-74.5) were assayed for 617 second chromosomes, and esterase-C (Est-C) and octanol dehydrogenase (Odh) were assayed for 526 third chromosomes. In addition, two polymorphic inversions in the second chromosomes [In(2L)t and In(2R)NS] were examined, and the following findings were obtained: (1) No linkage disequilibrium between isozyme genes was detected. Significant linkage disequilibria were found only between the polymorphic inversions and isozyme genes [In(2L)t vs. Adh, and In(2R)NS vs. Hex-C]. Significant disequilibrium was not detected between In(2L)t and alphaGpdh-1, which is included in the inversion, but a tendency toward disequilibrium was consistently found from 1968 to 1974. The frequency of two-strand double crossovers within inversion In(2L)t involving a single crossover on each side of alphaGpdh-1 was estimated to be 0.00022. Thus, the consistent but not significant linkage disequilibrium between the two factors can be explained by recombination after the inversion occurred. (2) Previously existing linkage disequilibrium between Adh and In(2R)NS (the distance is about 30 cM, but the effective recombination value is about 1.75%) was found to have disappeared. (3) No higher-order linkage disequilibrium was detected. (4) Linkage disequilibrium between Odh and Est-C (the distance of which was estimated to be 0.0058 +/- 0.002) could not be detected (chi(2) (df=1) = 0.9).-From the above results, it was concluded that linkage disequilibria among isozyme genes are very rare in D. melanogaster, so that the Franklin-Lewontin model (Franklin and Lewontin 1970) is not applicable to these genes. The linkage disequilibria between some isozyme genes and polymorphic inversions may be explained by founder effect.
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PMID:The genetic structure of natural populations of Drosophila melanogaster XIII. Further studies on linkage disequilibrium. 40 25

Type I hexokinase (ATP:D-hexose 6-phospotransferase, EC 2.7.1.1) of porcine heart exists in two chromatographically distinct forms. These do not differ significantly in size, electrophoretic mobility at pH 8.6 or kinetic properties. Both forms obey a sequential mechanism and are potently inhibited by glucose 6-phosphate. In contrast to observations of type I hexokinase from brain, inhibition by glucose 6-phosphate is not relieved by inorganic phosphate. Under most conditions, low concentrations of phosphate (less than 10 mM) have little effect on the kinetic behaviour of the enzyme but at higher concentrations this ligand is an inhibitor. Mannose 6-phosphate inhibits in a manner analogous to glucose 6-phosphate but the Ki is much greater. In view of the similarity of the kinetic parameters governing phosphorylation of mannose and glucose, this difference in affinity for the inhibitor site is seen as consistent with the existence of a separate regulatory site on the enzyme. MgADP inhibits hexokinase but behaves as a normal product inhibitor and inhibition is competitive with respect to MgATP and non-competitive with respect to glucose.
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PMID:Comparison of type I hexokinases from pig heart and kinetic evaluation of the effects of inhibitors. 42 Aug 59

Carbohydrate metabolism by four rat hepatoma cell lines in culture, namely, Reuber H35, MH1C1, RLC, and HTC, has been investigated. Glucose utilization by H35 and MH1C1 cells is lower than that by RLC and HTC cells. The four cell lines also differ with respect to the accumulation of lactic acid in the growth medium; in particular, H35 cells show uptake of lactic acid, rather than accumulation in the medium. Specific activities of a number of enzymes involved in glycolysis, gluconeogenesis, pentose phosphate pathway, and glycogen formation were determined in the four cell lines. A direct relationship between the differences was found for the activities of some enzymes belonging to carbohydrate metabolism, namely, hexokinase, pyruvate kinase, aldolases A and B, glucose-6-phosphate dehydrogenase, and phosphogluconate dehydrogenase and the differences found for glucose utilization by the different cell lines.
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PMID:Comparative studies of glucose metabolism in HTC, RLC, MH1C1, and Reuber H35 rat hepatoma cells. 42 45

The function of mitochondria-bound hexokinase, the enzymatic form peculiar to the brain, in utilization of ATP generated inside the organelles, was examined by incubating rat brain mitochondrial fraction with [14C]glucose under various conditions. Addition of succinate and ADP to the incubation medium increased glucose 6-phosphate formation by the mitochondrial hexokinase and caused a smaller increase in ATP concentration in the mitochondria. The glucose phosphorylation was markedly inhibited by the addition of dinitrophenol, potassium cyanide, and oligomycin, and the ATP concentration was decreased. On the other hand, addition of atractyloside suppressed the glucose phosphorylation without affecting the mitochondrial hexokinase activity, whereas addition of antiserum against the mitochondrial hexokinase inhibited both glucose 6-phosphate formation and hexokinase activity. A part of both the glucose phosphorylation and hexokinase activities, however, remained even in the presence of the maximum dose of the anti-hexokinase serum and atractyloside. These results indicate the active utilization of intrinsically generated ATP by the mitochondria-bound hexokinase, a part of which may be located away from the surface of the mitochondrial membrane.
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PMID:Functioning of mitochondria-bound hexokinase in rat brain in accordance with generation of ATP inside the organelle. 44 13


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