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)

The influence of clofibrate on the glycolytic pathway in liver was studied. The changes in the activity of glucokinase and hexokinase were not significant. A reduction of phosphofructokinase (p less than 0.05) and pyruvate kinase activity was found (p less than 0.0005) during clofibrate feeding. An in vitro inhibition of these enzymes could not be demonstrated by clofibrate up to a concentration of 2.5 mM. Crossover plots of glycolytic intermediates indicate that the reduced pyruvate kinase activity may influence the glycolytic pathway in vivo. Clofibrate feeding induces a lower ATP:ADP ratio, a lower adenylate energy charge and elevates AMP levels in rat liver. This may possibly stimulate the hepatic glycogenolysis and the glucose utilisation by this organ.
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PMID:Alterations of the glycolytic pathway and adenine nucleotide state in livers of clofibrate treated rats. 14 Aug 42

An extension of a previous model [2] is proposed of the glycolysis of erythrocytes which includes realistic rat laws for the hexokinase-phosphofructokinase system and for the 2,3-P2G phosphatase. Whereas most conclusions previously drawn are reinforced, the mechanism of ATP regulation is different in the present model. The ATP concentration is mainly regulated by the inhibitory action of ATP and the activating effect of AMP on the phosphofructokinase. The role of the 2,3-P2G bypass as a buffer of changes in the ATP demand is of lesser significance than previously thought. Besides the feedback action of the adenine nucleotides on the hexokinase-phosphofructokinase system in the quasisteady state the role of 2,3-P2G as an energy source is important since it can yield ATP for a certain period of time. The present version of the model describes qualitatively the experimental data on the modulation of Na+-K+-ATPase.
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PMID:An extended model of the glycolysis in erythrocytes. 14 74

From a 2.7-A resolution electron density map we have built a model of the polypeptide backbone of a monomer of yeast hexokinase B (EC 2.7.1.1). This map was obtained from a third crystal form of hexokinase, called BIII, which exhibits space group P212121 and which contains only one monomer per asymmetric unit. The 51,000 molecular weight monomer has an elongated shape (80 A by 55 A by 50 A) and is divided into two lobes by a deep central cleft. The polypeptide chain is folded into three structural domains, one of which is predominantly alpha-helical and two of which each contain a beta-pleated sheet flanked by alpha-helices. Both glucose and AMP bind to these crystals and produce significant alterations in the protein structure. Glucose binds in the deep cleft, as was observed previously in the BII crystal of the dimeric enzyme. AMP, however, binds to a site that is different from the major intersubunit ATP binding site observed in the crystalline dimer. The AMP is found near one of the beta-pleated sheets. From our current interpretation of this electron density map we conclude that neither of the two nucleotide binding regions has the same structure as has been observed for the nucleotide binding regions of the dehydrogenases, adenylate kinase, and phosphoglycerate kinase, although some similarities exist.
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PMID:The structure of a yeast hexokinase monomer and its complexes with substrates at 2.7-A resolution. 16 23

1. The concentration of adenylate kinase in carp muscle is about 0.3 mg/g. An improved isolation procedure makes use of a dilute solution of the substrates, ATP and AMP, to elute the enzyme from a phosphocellulose column in overall yields of 60% before crystallization. By the hexokinase--pH-stat assay the specific activity is 3550 units/mg. The preparation has been found to be essentially homogeneous by dodecylsulfate gel electrophoresis, isoelectrofocusing and gel filtration. 2. The molecular weight has been determined to be 22000 by several methods. The absorbance of a 1% solution at 280 nm is 6.9 and the isoelectric point by electrofocusing is pH 5.9. 3. The crystals of carp adenylate kinase have the space group P4-1-22 or P4-3-22. 4. The amino acid composition has been determined. There is no tryptophan, no cystine. There is one amino acid residue each of cysteine and histidine which are at or close to the catalytic center. 5. Several peptides derived by tryptic hydrolysis have been isolated and identified with corresponding peptides of porcine adenylate kinase. Consideration is given to histidine and cysteine being a part of the active site.
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PMID:Crystalline adenylate kinase from carp muscle. 16 48

In our studies of metabolic control mechanisms in skeletal muscle from rhesus fetus we have determined the tissue levels of the metabolic intermediates and cofactors of the glycolytic pathway and have calculated the mass-action ratios for each reaction. Skeletal muscle from rhesus fetuses (Macaca mulatta), 90-155 days of gestational age, and from adult rhesus monkeys was used in these experiments. The apparent equilibrium constants for hexokinase and phosphofructokinase (PFK) in these tissues were over 1,000 times larger than the mass-action ratios at all ages studied; the corresponding values for pyruvate kinase were more than 800 times different. The data suggest that these three enzymes are rate-limiting for fetal skeletal muscle as early as 54% of gestation. The next step was to study some of the numerous factors that modify these non-equilibrium reactions. Increasing the ATP concentration had a marked effect on the PFK activity of both fetal and adult muscle, first increasing and then inhibiting enzyme activity. At maximum PFK activity, the amount of fructose-6-PO4(F6P) phosphorylated per mg of protein was 2-3 times greater in the two fetal than in the adult series. At a concentration of 0.3 mM, citrate decreased PFK activity of the 100-day fetal muscle; a further decrease occurred at 1.2 mM citrate. At a citrate level of 0.3 mM. the addition of inorganic phosphate (Pi) or cyclic AMP returned PFK activity to the uninhibited levels (pH 7.0). Relief of ATP inhibition of F6P phosphorylation with Pi and cyclic AMP was also observed at pH 7.0 in extracts of 100-day fetal skeletal muscle.
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PMID:Control of glycolysis in skeletal muscle from fetal rhesus monkeys. 17 43

The investigations carried out have shown that not only AMP but ADP also undergoes direct deamination in both soluble and mitochondrial fractions of rat brain tissue. Deamination of AMP is stimulated by the addition of ATP and the activity of one of the isoenzymes of AMP-aminohydrolase is markedly enhanced by both yeast and brain hexokinase. Activation by hexokinase is mainly due to its SH groups, through which hexokinase reacts with AMP-aminohydrolase, forming, probably, a protein-protein complex in which AMP aminohydrolase activity is considerably increased. Hexokinase does not affect the deamination of ADP and NAD. Further experiments are needed to find out whether the activation of AMP-aminohydrolase is accomplished by hexokinase itself or by an other protein contaminating it. Deamination of NAD, in contrast to AMP and ADP, takes place only in mitochondria and does not occur in the soluble fraction. In mitochondria besides deamination, AMP and ADP undergo intensive dephosphorylation, while the deamination of NAD is not accompanied by an increase of phosphate, i. e. mitochondria lack enzymes which breakdown NAD to mono nucleotides. Our data indicate that the formation of deamino -NAD from NAD and reamination of deamino-NAD by aspartate to NAD by the formation of intermediary NAD-succinate is of greater importance. The formation of the latter and that of deamino-NAD from NAD as well as the presence of preformed deamino-NAD in mitochondria have been demonstrated by Movsessian. The occurrence of these processes in mitochondria and their role in the formation of ammonia from amino acids is of importance in as much as oxaloacetate formation and its conversion to aspartate, which is necessary for the reamination of deamino-NAD, are localized in mitochondria. The main source of the amino nitrogen of aspartate is known to be glutamate, which incorporates the amino nitrogen of most amino acids. alpha-Keto-glutarate, which is necessary for the synthesis of glutamate, is also formed in mitochondria are the most favourable site for the formation of ammonia from amino acids with the participation of pyridine nucleotides. Of the purine mono and dinucleotides studied deamino-NAD is most effective in the formation of ammonia from amino acids in mitochondria since in contrast to purine mono nucleotides, deamino-NAD and NAD are not dephosphorylated in mitochondria. According to some authors the reamination of IMP by aspartate is of importance in the formation of ammonia from amino acids in brain tissue. In our studies, however, IMP was not effective in the formation of ammonia from aspartate in mitochondrial fractions. IDP was found to be more effective. IMP and IDP may probably participate in the formation of ammonia in the soluble fraction, where nucleotidase activity is considerably low.
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PMID:[Role of adenine mono- and dinucleotides in ammonia formation in brain tissue]. 18 42

Nineteen derivatives of adenosine 5'-phosphate (AMP) bearing acylaminomethyl, acetoxy, or alkylaminomethyl substituents on the phosphate-ribose bridge (5' and O-5' positions) of AMP together with 2',3'-O-ethylidene, 2',3',-O-isopropylidene, and 2',3'-di-O-acetyl derivatives of AMP have been synthesized. Their substrate and/or competitive inhibitor properties with pig rabbit muscle AMP kinases indicate that all the substituents except 2',3'-O-ethlidene with the pig enzyme permitted binding of AMP at its enzymic site. Determination of enzyme-inhibitor dissociation constants showed that several compounds with substituents on the ribose-phosphate bridge bind as well or better than AMP. The affinity is ascribed in part to interaction between substituents and a lipophilic region of the enzymes adjacent to the ribose-phosphate bridge in the enzyme-AMP complexes. The enzyme-inhibitor dissociation constants reveal a structural dissimilarity between the pig and rabbit enzymes in the vicinity of the lipophilic region. The substrate and inhibitor properties of eight ATP derivatives gave evidence that affinity of ATP for its substrate site on the AMP kinases is compatible with acetyl- or chloroacetylaminomethyl groups at the phosphate-ribose bridge or with 2',3'-O-ethylidene or isopropylidene residues. The yeast hexokinase-ATP complex tolerated an acetylaminomethyl group at C-5' or a benzoylaminomethyl group adjacent to O-5'. The present findings regarding substituent tolerance could be used in the design of adenine nucleotide site-directed irreversible inhibitors.
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PMID:Design of substrate-site-directed inhibitors of adenylate kinase and hexokinase. Effect of substrate substituents on affinity on affinity for the adenine nucleotide sites. 18 50

Reaction of ADP with hexamethylene diisocyanate in hexamethylphosphoramide followed by treatment in an acidic medium afforded three new adenine nucleotide analogues, N6-[N-(6-aminohexyl)carbamoyl]-ADP, N6-[N-(6-aminohexyl)carbamoyl]-ATP, and N6-[N-(6-aminohexyl)carbamoyl]-AMP in yields of 13%, 12% and 17%, respectively. The occurrence of the ATP analogue may be interpreted in terms of the equilibrium, 2ADP = ATP + AMP. Coenzymic activities of the ADP analogue against acetate kinase and pyruvate kinase were 82% and 20%, respectively, relative to ADP and those of the ATP analogue against hexokinase and glycerokinase were 63% and 87%, respectively, relative to ATP. These analogues were bound to CNBr-activated soluble dextran through their terminal amino group to give an immobilized ADP and an immobilized ATP, each of which was recycled in a system comprising acetate kinase and hexokinase, and when placed in a membrane reactor together with the enzymes, functioned as an immobilized coenzyme continuously yielding glucose 6-phosphate. A series of chemically defined affinity adsorbents were obtained by coupling these analogues to CNBr-activated Sepharose, and were used to separate the enzymes in a mixture of hexokinase, pyruvate kinase, phosphoglycerate kinase, lactate dehydrogenase, and alcohol dehydrogenase.
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PMID:Preparation of N6-[N-(6-aminohexyl) carbamoyl]-adenine nucleotides and their application to coenzymically active immobilized ADP and ATP, and affinity adsorbents. 19 56

Based on previous studies which have revealed that glucose 1,6-bisphosphate (Glc-1,6-P2) is a potent inhibitor of muscle hexokinase and an activator (deinhibitor) of phosphofructokinase and phosphoglucomutase, the effect of epinephrine on the levels of this regulator in rat diaphragm muscle was investigated. It was found that epinephrine caused an increase in diaphragm Glc-1,6-P2 levels, accompanied by a reduction in the activity of hexokinase and an activation (deinhibition) of phosphofructokinase and phosphoglucomutase. N6-2'-O-dibutyryl cyclic AMP was able to mimic all these effects of epinephrine. The concentration of glucose-6-phosphate was not changed by epinephrine, under conditions in which the hormone produced an increase in cyclic AMP and Glc-1,6-P2 levels and the concomitant decrease in hexokinase activity. It was also shown that Glc-1,6-P, in the concentration range found after epinephrine, inhibited the diaphragm hexokinase and deinhibited phosphoglucomutase. These results may suggest a mechanism of epinephrine action by which the activities of hexokinase, phosphoglucomutase and phosphofructokinase, through the action of Glc-1,6-P2, are synchronized with the cyclic AMP-mediated activation of glycogen phosphorylase, to achieve an increase in total glycogenolysis and glycolysis and a concomitant reduction in glucose utilization by the muscle.
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PMID:The effect of epinephrine and dibutyryl cyclic AMP on glucose 1,6-bisphosphate levels and the activities of hexokinase, phosphofructokinase and phosphoglucomutase in the isolated rat diaphragm. 20 4

Reaction of AMP with formaldehyde and 3-mercaptopropionic acid at pH 11.7 gave a new AMP derivative, N6-[(2-carboxyethyl)thiomethyl]-AMP (I) in 91% yield and reaction at pH 3.1 gave another new derivative, N6,N6-bis[(2-carboxyethyl)thiomethyl]-AMP (II) in 57% yield. The structures were determined by their 13C and 1H nuclear magnetic resonance spectra coupled with those of the simple analogues, N6-[(2-carboxyethyl)thiomethyl]-9-methyladenine (III) and N6,N6-bis[(2-carboxyethyl)thiomethyl]-9-methyladenine (IV) which were synthesized from 9-methyladenine in the same way as for derivatives I and II. ADP and ATP were treated in the same way as AMP to afford the corresponding carboxyl derivatives, N6-[(2-carboxyethyl)thiomethyl]-ADP (V), N6-[(2-carboxyethyl)thiomethyl]-ATP (VI), N6,N6-bis[(2-carboxyethyl)thiomethyl]-ADP (X) and N6,N6-bis[(2-carboxyethyl)thiomethyl]-ATP (XI) in 71%, 75%, 53% and 40% yield, respectively. These compounds were coupled to 1,3-diaminopropane with a water-soluble carbodiimide to give the corresponding amino derivatives, N6-([N-3-aminopropyl)carbamoylethyl]thiomethyl)-ADP (VIII), N6-(N-(3-aminopropyl)carbamoylethyl]thiomethyl)-ATP (IX), N6,N6-bis([N-(3-aminopropyl)carbamoylethyl]thiomethyl)-ADP (XIII), and N6,N6-bis([N-(3-aminopropyl)carbamoylethyl]thiomethyl)-ATP (XIV), which were further bound to CNBr-activated dextran to give new polymer-bound derivatives of ADP and ATP. These free and bo-nd derivatives were tested for their coenzymic activities against several kinases. The activities of the ADP derivatives, V, VIII, X, XIII, dextran-bound VIII, and dextran-bound XIII against acetate kinase were 82%, 81%, 68%, 55%, 35%, and 15%, respectively, relative to ADP and those of the ATP derivatives, VI, IX, XI, XIV, dextran-bound IX, and dextran-bound XIV against hexokinase were 88%, 94%, 60%, 81%, 58%, and 49%, respectively, relative to ATP.
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PMID:A new method of chemical modification of N6-amino group in adenine nucleotides with formaldehyde and a thiol and its application to preparing immobilized ADP and ATP. 21 8


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