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[Effect of oxygen on the transformation of ribulose-1,5-diphosphate in the hydrogen bacterium Hydrogenomonas eutropha].

Oxygenase transforamtion of ribulose-1,5-diphosphate was found in the hydrogen bacterium Hydrogenomonas eutropha Z-1. Oxygen inhibits the carboxylating activity of ribulose-1,5-diphosphate carboxylase by 42% at a low concentration of the substrate of carboxylation--bicarbonate. The oxygenase activity of this carboxylase is saturated at 50% of oxygen in the atmosphere.

Bicarbonates↗
PubMed1993

[The effect of fructose-1,6-diphosphate and phosphoenolpyruvate on the course of early occlusion and reperfusion arrhythmias in rats].

Fructose-1,6-diphosphate (150 and 50 mg/kg) and phosphoenolpyruvate (0.5 and 0.1 mg/kg) decreased the development of ventricular tachycardia, ventricular fibrillation and the intensity of ventricular extrasystoles after coronary occlusion in experimental rats. Both compounds were active as anti-fibrillation agents on reperfusion arrhythmias. Fructose-1,6-diphosphate potentiated the effect of lidocaine.

Animals↗
PubMed1993

Complementary deoxyribonucleic acid cloning and expression of a human liver uridine diphosphate-glucuronosyltransferase glucuronidating carboxylic acid-containing drugs.

A cDNA clone, designated UGT2B7 variant, encoding a 529-amino acid human liver microsomal uridine diphosphate-glucuronosyltransferase (UGT) was isolated from a lambda gt11 human liver cDNA library. UGT2B7 variant synthesized in COS-7 cells was screened for activity toward a range of clinically used drugs and other xenobiotics. The expressed enzyme glucuronidated several carboxylic acid-containing nonsteroidal antiinflammatory agents including, in order of relative substrate activity, naproxen, ketoprofen, ibuprofen, fenoprofen, tiaprofenic acid, benoxprofen, zomepirac, diflunisal and indomethacin. Additionally, the stereoselectivity of ketoprofen, naproxen (S/R ratio approximately unity) and ibuprofen (S/R ratio 1.62) glucuronidation by the UGT2B7 variant was shown to differ. Two other carboxylic acid-containing drugs (clofibric acid and valproic acid) and a limited range of drugs containing an alcohol or phenolic functional group were also glucoronidated by expressed UGT2B7 variant. The deduced amino sequence of UGT2B7 variant was shown to differ only in one amino acid (tyrosine for histidine at position 268) from a previously published uridine diphosphate-glucuronosyltransferase cDNA, UGT2B7. Like the previously reported enzyme, this variant efficiently glucuronidated hyodeoxycholic acid, estriol, 4-hydroxyestrone and 2-hydroxyestriol. It is, therefore, apparent that UGT2B7 variant has the capacity to glucuronidate with a degree of specificity both endogenous compounds and xenobiotics. Preferred substrates for UGT2B7 variant include xenobiotic carboxylic acids, polyhydroxylated estrogens and hyodeoxycholic acid.

Animals↗
PubMed1995

In vitro inhibition of rat heart sarcoplasmic reticular membrane ATPase activities by amphotericin B and their reversal by fructose-1,6-diphosphate.

The effect of amphotericin B on rat heart sarcoplasmic reticular membrane Na(+)-K+ and Ca2+ ATPase activities in vitro was investigated. Amphotericin B in selected concentrations of 100-1000 ng significantly inhibited the sarcoplasmic reticular membrane ATPase activities studied. Fructose-1,6-diphosphate (1000 microM concentration) completely reversed the inhibition of Ca2+ ATPase activity in particular, but failed to reverse that of Na+(-)K+ATPase activities at 1000 microM concentration. Fructose-1,6-diphosphate may afford some protection against 1000 ng amphotericin B-induced myocardial toxicity. These damages may vary depending upon the dose of amphotericin B used in experimental studies.

Adenosine Triphosphatases↗
PubMed1998

1-beta-D-Arabinofuranosylcytosine-5'-alkylphosphonophosphates and diphosphates: new orally active derivatives of ara-C.

ara-Cytidine-5'-alkylphosphonophosphates and the corresponding -diphosphates were found to be cytostatically active in vitro against the human mammary epithelial cell line H184 A1N4 and the human mammary tumor cell line MaTu. Our results indicate that the replacement of the diphosphate by the phosphonophosphate group has no influence on antiproliferative activity in this case. The compounds were more active than the corresponding cytidine phospholipid conjugates and related compounds lacking a cytostatically active nucleoside, the ara-C prodrug Cytoros, and were slightly less active than ara-C. The cytostatic effect was prevented by 2'-deoxycytidine indicating their action as prodrugs of ara-C. In contrast to ara-C, they increase [Ca2+]1 in H184 A1N4 cells, pointing to a different mechanism of action in addition to their prodrug effect. In combination with phospholipid analogs, synergistic effects could be observed. Further studies within the disease-oriented in vitro Anticancer Screening Program of the National Cancer Institute show selectivity for certain cancer cell lines. The hexadecyl derivatives revealed a significant antitumor activity in vivo against the murine lymphatic leukemia P 388 cells being equally potent or even superior to ara-C. In contrast to ara-C, they were found to be orally active. Side effects measured as leukopenia and body weight reduction were less pronounced than with the parent drug.

Animals↗
PubMed1997

nm23-H4, a new member of the family of human nm23/nucleoside diphosphate kinase genes localised on chromosome 16p13.

A novel human nm23/nucleoside diphosphate (NDP) kinase gene, called nm23-H4, was identified by screening a human stomach cDNA library with a probe generated by amplification by reverse transcription-polymerase chain reaction. The primers were designed from publicly available database cDNA sequences selected according to their homology to the human nn23-H1 putative metastasis suppressor gene. The full-length cDNA sequence predicts a 187 amino acid protein possessing the region homologous to NDP kinases with all residues crucial for nucleotide binding and catalysis, strongly suggesting that Nm23-H4 possesses NDP kinase activity. It shares 56, 55 and 60% identity with Nm23-H1, Nm23-H2 and DR-Nm23, respectively, the other human Nm23 proteins isolated so far. Compared with these proteins, Nm23-H4 contains an additional NH2-terminal region that is rich in positively charged residues and could indicate routing to mitochondria. The nm23-H4 gene has been localised to human chromosomal band 16p13.3. The corresponding 1.2 kb mRNA is widely distributed and expressed in a tissue-dependent manner, being found at very high levels in prostate, heart, liver, small intestine and skeletal muscle tissues and in low amounts in the brain and in blood leucocytes. Nm23-H4 naturally possesses the Pro-Ser substitution equivalent to the K-pn mutation (P97S) of Drosophila.

Amino Acid Sequence↗
PubMed1989

Activation of rat liver cytosolic phosphatidic acid phosphatase by nucleoside diphosphates.

Phosphatidic acid phosphatase (EC 3.1.3.4) was purified 30-fold by ammonium sulfate fractionation and hydroxyapatite chromatography from the soluble fraction of rat liver. ADP was found to stimulate the enzyme activity with half-maximal stimulation at 0.2 mM. Similar effects were seen when ADP was replaced by GDP or CDP. In contrast, ATP inhibited the enzyme; half-maximal inhibition observed at 0.2 mM. Again, the degree of inhibition did not differ when GTP or CTP replaced ATP. Thus, the structure of the base part of the nucleotide was not critical for mediating these effects. The positions of the phosphate groups in the nucleotide structure were however found to be of importance for the enzyme activity. Variations in the structure of the phosphate ester bound at the 5'-position had a pronounced effect on phosphatidic acid phosphatase activity. The effect of nucleotides depended on pH, and the inhibition by ATP was more pronounced at pH levels lower than 7.0, whereas the stimulatory effect of ADP was virtually the same from pH 6.0 to pH 8.0. The enzyme showed substrate saturation kinetics with respect to phosphatidic acid, with an apparent Km of 0.7 mM. Km increased in the presence of ATP, whereas both apparent Vmax and Km increased in the presence of ADP, suggesting different mechanisms for the action of the two types of nucleotides. The results indicated that physiological levels of nucleotides with a diphosphate or a triphosphate ester bound at the 5'-position of the ribose moiety influenced the activity of phosphatidic acid phosphatase. The possibility is discussed that these effects might be of importance for the regulation of triacylglycerol biosynthesis.

Adenosine Diphosphate↗
PubMed1979

A method for the synthesis of oligonucleotide by single addition of 2'-O-(o-nitrobenzyl)nucleoside 5'-diphosphates using polynucleotide phosphorylase.

Two hexanucleotides A-U-G-U-G-A and C-A-A-U-U-G were synthesized from the chemically synthesized trimers C-A-A and A-U-G by addition of 2'-O-(o-nitrobenzyl)nucleoside diphosphates using polynucleotide phosphorylase isolated from either Escherichia coli or Micrococcus luteus. In each reaction the preference of the enzyme was tested. The o-nitrobenzyl group was removed after addition of the mononucleotide and the deblocked product was isolated by chromatography on DEAE-Sephadex in high yields.

Adenosine Diphosphate↗
PubMed1999

Nucleoside diphosphate kinase associated with membranes modulates mu-opioid receptor-mediated [35S]GTPgammaS binding and agonist binding to mu-opioid receptor.

The role of nucleoside diphosphate kinase (NDKP), which converts GDP to GTP, in the coupling of mu-opioid receptors to G protein was investigated in membranes of Chinese hamster ovary cells stably transfected with the cloned rat mu-opioid receptor (rmor). Endogenous NDPK activity in membranes was determined to be 0.60+/-0.02 micromol/mg protein/30 min UDP (at 10 mM), a competitive substrate of NDPK for GDP with no effect on guanine nucleotide binding to G proteins, reduced basal [35S]GTPgammaS binding and unmasked morphine-stimulated [35S]GTPgammaS binding to pertussis toxin-sensitive G proteins, indicating that [35S]GTPgammaS binding to NDPK accounts for part of its high basal binding. UDP increased the extent of morphine-induced increase in [35S]GTPgammaS binding in the presence of GDP, most likely by reducing basal binding and inhibiting conversion of GDP to GTP. ATP greatly reduced morphine-induced increase in [35S]GTPgammaS binding, whereas AMP-PCP (adenylyl-(beta,gamma-methylene)-diphosphoate tetralithium salt), which cannot serve as the phosphate donor for NDPK, did not, demonstrating that effects of ATP is mediated by the NDPK product GTP. In addition, GDP and ATP increased the Kd and lowered the Bmax of the agonist [3H]DAMGO ([D-Ala2,N-Me-Phe4,Gly5ol]-Enkephalin) for the mu-opioid receptor and GDP alone increased Kd, most likely through their conversion to GTP by NDPK. Addition of exogenous NDPK enhanced the inhibitory effects of GDP and combined GDP and ATP on [3H]DAMGO binding. Thus, NDPK appears to play a role in modulating signal transduction of and agonist binding to mu-opioid receptors.

Adenosine Triphosphate↗
PubMed1993

Estimates of uridine diphosphate hexoses in erythrocytes: implications for galactosemia.

Impurities in a reagent dehydrogenase caused overestimates of erythrocytic uridine diphosphate glucose and accounted for clinically important differences in results between those of one group of investigators using enzymatic methods and those of two other groups using enzymatic methods, high-performance liquid chromatography, and nuclear magnetic resonance. These data have relevance for the current debate regarding the pathophysiologic changes in galactosemia.

Drug Contamination↗
PubMed1995

X-ray structure of human nucleoside diphosphate kinase B complexed with GDP at 2 A resolution.

BACKGROUND: Nucleoside diphosphate (NDP) kinases provide precursors for DNA and RNA synthesis. In mammals, these enzymes are also involved in cell regulations. Human NDP kinase B, product of the human nm23-H2 gene, is both an enzyme and a transcription factor. It activates transcription of the c-myc oncogene independently of its catalytic function, by binding to its promoter DNA. How do the two functions coexist? RESULTS: Recombinant human NDP kinase B was co-crystallized with GDP. The X-ray structure was solved at 2.0 A resolution by molecular replacement from the homologous Drosophila Awd protein. Both enzymes are homo-hexamers with a characteristic beta alpha beta beta alpha beta fold. GDP binds near the active site His118. The guanine base is in a surface cleft and interacts with the C terminus of another subunit. CONCLUSIONS: The beta alpha beta beta alpha beta fold, also present in the 'palm' domain of Escherichia coli DNA polymerase I and HIV reverse transcriptase, is both a mononucleotide- and a polynucleotide-binding fold. If NDP kinase B binds DNA in the same way as the polymerases, the enzyme must undergo a conformation change in order to carry out gene activation.

Amino Acid Sequence↗
PubMed1975

Uridine diphosphate glucose synthase from calf liver: determinants of enzyme activity in vitro.

The reaction catalyzed by calf liver uridine diphosphate glucose synthase (pyrophosphorylase) (EC 2.7.7.9; UTP + glucose 1-phosphate = UDP-glucose + PPi) is an example of an enzymic reaction in which a nucleoside triphosphate other than ATP is the immediate source of metabolic energy. Kinetic properties of the enzyme, acting in the direction of UCP-glucose formation were investigated in vitro. The reaction was inhibited by UDP-glucose (0.072), Pi (11), UDP (1.6), UDP-xylose (0.87), UDP-glucuronate (1.3), and UDP-galacturonate (0.95). The numbers in parentheses indicate the concentration (mM) required for half-maximal inhibition under the conditions used. Other compounds tested, including ATP, ADP, and AMP, had no effect. Over a range of concentrations of UTP (0.04-0.8 MM) and UDP-glucose (0.05-0.03 mM), the reaction rate was more dependent on the concentration ratio [UDP-glucose]/[UTP] than on the absolute concentration of either compound. Comparison of the kinetic properties in vitro with estimates of metabolite levels in vivo suggests that (1) the enzyme operates in a range far from its maximal rate, and (2) the concentrations of glucose 1-phosphate and Pi and the ratio [UDP-glucose]/[UTP] may be the most important determinants of UDP-glucose synthase activity.

Adenine Nucleotides↗
PubMed1977

Changes in enzymic activities of nucleoside diphosphate sugar interconversions during differentiation of cambium to xylem in sycamore and poplar.

During the transition from primary wall formation to secondary thickening there is a marked shift in the synthesis of pectin, hemicellulose and cellulose. The activities of the enzymes [UDP-D-galactose 4-epimerase (EC 5.1.3.2)8 UDP-l-arabinose 4-epimerase (EC 5.1.3.5), UDP-D-glucose dehydrogenase (EC 1.1.1.22) and UDP-D--glucuronate decarboxylase (EC 4.1.1.35)] were measured in cambial cells, differentiating xylem cells and differentiated xylem cells isolated from sycamore and poplar trees, and phloem cells from poplar. At the final stage of the differentiation of cambium to xylem there was a decrease in activity of the enzymes directly involved in producing the soluble precursors of pectin (DUP-D-galactose 4-epimerase and UDP-L-arabinose 4-epimerase and an increase in those producing the precursors of hemicellulose (UDP-D-glucose dehydrogenase and UDP-D-glucuronate decarboxylase). These results strongly suggest ahat the changes were correlated with the differences observed in the chemical composition of the wall during development. The changes found in the catalytic activity of the enzymes of nucleoside diphosphate sugar interconversion exert a coarse control over the synthesis of pectin and hemicelluloses. The tissues at all stages of development contained the necessary enzyme activities to produce all the precursors of pectin and hemicellulose, even at the final stage of differentiation when no pectin was formed.

Arabinose↗
PubMed1977

Changes in enzymic activities of nucleoside diphosphate sugar interconversions during differentiation of cambium to xylem in pine and fir.

A protein fraction [precipitate obtained between 40 and 65% (NH4)2SO4 satn.] prepared from cambial cells, differentiating xylem cells and differentiated xylem cells of pine and fir trees contained all the enzymes required for the nucleoside diphosphate sugar interconversions. By using UDP-D-[U-14C]glucose or UDP-D-[U-14C]galactose, UDP-D-[U-14C-]glucuronic acid and UDP-D-[U-14C]xylose as substrates, the activities of UDP-D-galactose 4-epimerase (DC 5.1.3.2), UDP-D-xylose 4-epimerase(EC 5.1.3.5), UDP-D-glucose dehydrogenase (EC 1.1.1.22) and UDP-D-glucuronate 4-epimerase (EC5.1.3.6), UDP-d-glucuronate decarboxylase (EC 4.1.1.35) were measured at different stages of cell-wall development. The specific activities and the activities per cell of these enzymes varied during differentiation of cambium to xylem according to the type polysaccharide synthesized. Variations were also found between the two species investigated. These data, compared with those obtained in out previous work on angiosperms [see the preceding paper, Dalessandro & Northcote (1977) Biochem. J. 162, 267-279], suggest that some control of polysaccharide synthesis operates at the level of the formation of the precursors of pectin and hemicellulose syntheses.

Carbohydrate Epimerases↗
PubMed1987

The role of C-4-substituted mannose analogues in protein glycosylation. Effect of the guanosine diphosphate esters of 4-deoxy-4-fluoro-D-mannose and 4-deoxy-D-mannose on lipid-linked oligosaccharide assembly.

The effects of the guanosine diphosphate esters of 4-deoxy-4-fluoro-D-mannose (GDP-4FMan) and 4-deoxy-D-mannose (GDP-4dMan) on reactions of the dolichol pathway in chick-embryo cell microsomal membranes were investigated by studies with chick-embryo cell microsomal membranes in vitro and in baby-hamster kidney (BHK) cells in vivo. Each nucleotide sugar analogue inhibited lipid-linked oligosaccharide biosynthesis in a concentration-dependent manner. GDP-4FMan blocked in vitro the addition of mannose to Dol-PP-(GlcNAc)2Man from GDP-Man (where Dol represents dolichol), but did not interfere with the formation of Dol-P-Man, Dol-P-Glc and Dol-PP-(GlcNAc)2. Although GDP-4FMan and Dol-P-4FMan were identified as metabolites of 4FMan in BHK cells labelled with [1-14C]4FMan, GDP-4FMan was a very poor substrate for GDP-Man:Dol-P mannosyltransferase and Dol-P-4FMan could only be synthesized in vitro if the chick-embryo cell membranes were primed with Dol-P. It therefore appears that the inhibition of lipid-linked oligosaccharide formation in BHK cells treated with 4FMan [Grier & Rasmussen (1984) J. Biol. Chem. 259, 1027-1030] is due primarily to a blockage in the formation of Dol-PP-(GlcNAc)2Man2 by GDP-4FMan. In contrast, GDP-4dMan was a substrate for those mannosyltransferases that catalyse the transfer of the first five mannose residues to Dol-PP-(GlcNAc)2. In addition, GDP-4dMan was a substrate for GDP-Man:Dol-P mannosyltransferase, which catalysed the formation of Dol-P-4dMan. As a consequence of this, the formation of Dol-P-Man, Dol-P-Glc and Dol-PP-(GlcNAc)2 may be inhibited through competition for Dol-P. In BHK cells treated with 10 mM-4dMan, Dol-PP-(GlcNAc)2Man9 was the major lipid-linked oligosaccharide detected. Nearly normal extents of protein glycosylation were observed, but very little processing to complex oligosaccharides occurred, and the high-mannose structures were smaller than in untreated cells.

Animals↗
PubMed1999

Intrinsic nucleoside diphosphate kinase-like activity is a novel function of the 20 S proteasome.

The eukaryotic 20 S proteasome is the prototype of a new family of the N-terminal nucleophil hydrolases and is composed of numerous low molecular mass subunits arranged in a stack of four rings, each containing seven different alpha- or beta-subunits. Among the beta-type subunits in the yeast proteasome, three proteolytically active ones were identified, although the functions of the other beta- and alpha-type subunits remain to be clarified. We report here that the purified 20 S proteasome exhibits intrinsic nucleoside diphosphate (NDP) kinase-like activity. The proteasome exhibited a preference for ATP and dATP as phosphate donors, and a broad specificity for NDPs, other than GDP, as phosphate acceptors, unlike conventional NDP kinase, which catalyzes the transfer of gamma-phosphate between NDPs and nucleoside triphosphates. During the transfer of gamma-phosphate, the proteasome formed acid-labile phosphohistidine as autophosphorylated intermediates, and NDP-dependent dephosphorylation of the latter then occurred. These enzymatic properties are similar to those of the molecular chaperone, Hsp70, which also exhibits intrinsic NDP kinase-like activity, instead of ATPase activity. C5 among the beta-type subunits and C8 among the alpha-type subunits were autophosphorylated during the gamma-phosphate transfer reaction and were photoaffinity labeled with 8-azido-[alpha-(32)P]ATP, suggesting that the C5 and C8 subunits of the proteasome are responsible for the NDP kinase-like activity.

Adenosine Diphosphate↗