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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Organic pyrophosphates such as UppA and NAD are formed when a solution containing a nucleotide, a nucleoside 5'-polyphosphate, Mg2+ and imidazole are allowed to dry out. We suggest that this synthesis may have occured concurrently with oligonucleotide formation.
J Mol Evol 1978 May 12
PMID:Formation of P1, P2-dinucleoside 5'-pyrophosphates under potentially prebiological conditions. 20 76

Lactate dehydrogenase and glycerol 3-phosphate dehydrogenase are metabolically coupled by the anaerobic dismutation of glyceraldehyde 3-phosphate and by the NAD redox state. This causes the concentrations of lactate and glycerol 3-phosphate to accumulate proportionally during anaerobic muscle contraction; these concentrations are high relative to those in aerobic tissues such as liver. We show that the isoenzymes of lactate dehydrogenase and glycerol 3-phosphate dehydrogenase from chicken breast muscle have Km values for lactate and glycerol 3-phosphate, respectively, that are 10-fold higher than the Km values measured for the lactate dehydrogenase and glycerol 3-phosphate dehydrogenase isoenzymes from chicken liver. The association of proportionally higher Km values with the potential for proportionally higher accumulation of substrates suggests that the isoenzymes of lactate dehydrogenase and glycerol 3-phosphate dehydrogenase from chicken muscle have evolved in parallel as a coupled metabolic unit distinct from the coupled isoenzymes in liver. The parallelism observed for the reduced substrates extends to the oxidized substrates, and to the coenzymes, NAD+ and NADH.
J Mol Evol 1978 May 12
PMID:Parallel evolution of pairs of dehydrogenase isoenzymes. 20 78

New theoretical considerations and a new approximation strategy were applied to the kinetic analysis of the experimental relationship between the reaction velocity in the steady state and the concentrations of ethanol and NAD. It could be shown that horse-liver ADH consists of two kinetically heterogeneous components.
Mol Cell Biochem 1978 May 31
PMID:Steady-state study of horse-liver ADH: detection of two kinetically heterogeneous components. 20 74

Some considerations concerning the detailed mechanism of negative cooperativity in GPD are proposed. The hypothesis represents a modification of the sequential model (Koshland et al.) taking into account last experimental data about the binding of NAD analogs and fragments. Two main facts have been used as a basis for the model: 1. Neither ADP-ribose nor nicotinamide mononucleotide (NMN) fragments of NAD show negative cooperative binding to GPD. 2. Neither modifications of adenine and nicotinamide part of NAD (epsilon-NAD, hypoxantine-NAD, oxidized and reduced-NAD) nor enzyme modifications by various reagents acting in the catalytic site affect considerably the cooperativity of coenzyme binding although the affinity between enzyme and coenzyme (analogs) substantially changes depending on the nature of modification. Probably the structural integrity of a coenzyme molecule is necessary for the cooperative binding to GPD. On the other hand, numerous modification studies can be interpreted as proving the absence of direct participation of adenine and nicotinamide rings in the mechanism of negative interactions between NAD-binding sites. It appears reasonable to assume that direct or indirect interactions of riboseAD and pyrophosphate groups of NAD with the "loop" of adjacent subunit might be necessary for the tight coenzyme binding to the first active site of the r-dimer(s) symmetric across the R-axis. After the tight binding of the first NAD molecule on r-dimer with the "loop" participation, the symmetrical movement of second "loop" might be highly restricted. It was postulated that only asymmetric conformational transition is possible in contact areas between subunits across the R-axis. Such asymmetric rearrangement can explain the nonequivalent binding of NAD to a prior symmetric dimmer(s).
Mol Biol (Mosk)
PMID:[Possible nature of negative cooperation in D-glyceraldehyde-3-phosphate dehydrogenase]. 22 1

Nuclei isolated from D. discoideum and incubated in vitro with 3H-NAD synthesise poly(ADP-Rib). The optimum incubation conditions for the poly(ADP-Rib) polymerase were determined. The Km of the enzyme is 18 microM NAD and it is inhibited by nicotinamide. Most of the poly(ADP-Rib) synthesised is attached to nuclear proteins.
Mol Cell Biochem 1979 Oct 15
PMID:Characterisation of poly(ADP-Rib) polymerase activity in nuclei from the slime mould Dictyostelium discoideum. 22 76

Conservation of polypeptide fold and mode of ligand binding is frequently found within proteins of related function. Examples illustrating this phenomenon are taken from NAD linked enzymes, nucleotide binding proteins, polysaccharide binding proteins, heme binding proteins and enzymes with essential Fe--S complexes or zinc atoms.
Mol Cell Biochem 1978 Nov 16
PMID:The taxonomy of binding sites in proteins. 36 87

Partially purified flounder muscle (Pseudopleuronectus americanus) glyceraldehyde 3-phosphate dehydrogenase was immobilized on cyanogen bromide-activated Sepharose. The catalytic properties of the immobilized preparation were studied to determine if immobilization alters the kinetic properties of the native holoenzyme. The results indicate that the pH activity profile of immobilized glyceraldehyde 3-phosphate dehydrogenase did not differ from that of the native enzyme. The Michaelis constants (Km) for NAD and glyceraldehyde 3-phosphate were somewhat altered. The enzyme stability toward various inactivation treatments in the presence and absence of NAD was characterized and compared to that of he native enzyme. When either form of the enzyme was incubated with urea at concentrations greater than 2M, inactivation occurred very rapidly. Incubation in 0.1% trypsin for 60 minutes decreased the activity of immobilized glyceraldehyde 3-phosphate dehydrogenase by 45% and of the native soluble enzyme by 70%. The immobilized enzyme also exhibited considerably more stability than the native soluble enzyme when exposed to a temperature of 50 degrees or to 20 mM ATP. In all cases NAD either greatly reduced the rate of inactivation or completely protected the enzyme from inactivation.
Mol Cell Biochem 1978 Nov 16
PMID:Immobilized flounder muscle glyceraldehyde 3-phosphate dehydrogenase. 56 63

The activities of isocitrate dehydrogenase (NAD), isocitrate dehydrogenase (NADP) and oxoglutarate dehydrogenase have been investigated in Saccharomyces cerevisiae grown in a variety of aerobic and hypoxic conditions, the latter including oxygen deprivation, high glucose concentration, addition of inhibitors of mitochondrial protein synthesis, respiratory inhibition by azide, and impaired respiration mutants. All hypoxic conditions led to a marked decrease of oxoglutarate dehydrogenase and significant decreases of the two isocitrate dehydrogenases. According to its kinetic properties, the NAD-isocitrate dehydrogenase will not be operative in hypoxia "in vivo". From these and other related facts it is concluded that hypoxic conditions in yeast generally lead to a splitting of the tricarboxylic acid cycle and that glutamate synthesis in these conditions takes place through the coupling of the NADP-linked isocitrate and glutamate dehydrogenases.
Mol Cell Biochem 1975 Feb 28
PMID:Isocitrate dehydrogenases and oxoglutarate dehydrogenase activities of baker's yeast grown in a variety of hypoxic conditions. 109 51

Platelet-activating factor (PAF) is an unusually potent phospholipid known to be produced by neuronal cells and to modulate cerebral blood flow and metabolism. In previous studies with NCB-20 cells, we reported that PAF induced a significant mobilization of intracellular free Ca2+ ([Ca2+]i), which was inhibited by PAF antagonists. The increase was the result of release from intracellular stores and influx from extracellular sources. The present study was designed to characterize further PAF receptor-mediated cellular signal-transduction mechanisms in myo-[3H]inositol-labeled cells. PAF induced a concentration-dependent increase in phosphatidylinositol (Pl) metabolism, with EC50 values of 1.96 +/- 0.62 nM and 1.12 +/- 0.50 nM for inositol trisphosphate (IP3) and inositol monophosphate (IP1) formation, respectively (four experiments). The maximal production of IP3 and IP1 induced by 50 nM PAF was 254 +/- 34% and 178 +/- 25% over the basal, respectively (four experiments). PAF-induced Pl metabolism was concentration-dependently inhibited by the PAF antagonist BN50739, with an IC50 value of 6.48 +/- 0.52 nM (four experiments). The protein kinase C (PKC) activator phorbol 12,13-dibutyrate concentration-dependently inhibited PAF-induced Pl metabolism and [Ca2+]i mobilization in NCB-20 cells, of NCB-20 cells with pertussis toxin (PTX) resulted in a concentration-dependent inhibition of PAF-induced IP3 production and intracellular Ca2+ release, with a maximal reduction of 66.9 +/- 3.5% and 63 +/- 6.1%, respectively, at 300 ng/ml PTX. PTX in the presence of [32P]NAD specifically [32P]ADP-ribosylated a 38-kDa protein in membranes prepared from NCB-20 cells. Pretreatment of the cells with PTX resulted in a concentration-dependent inhibition of subsequent 32P-labeling of the toxin substrate in the membranes and correlated with the uncoupling of PAF-induced IP3 formation. PAF (0.01-10 nM) elicited a concentration-related stimulation in guanosine 5'-O-(3-[35S]) triphosphate ([35S]GTP gamma S) binding to G alpha i(1,2) proteins, which was inhibited by the PAF antagonist BN50739. PAF at 10 nM also increased [35S]GTP gamma S binding to G alpha s and G alpha o. PAF-evoked activation of G alpha i(1,2) and G alpha o was reduced by preincubation with PTX. Our results reveal that neuronal cells possess PAF receptors linked through guanine nucleotide-binding proteins to phospholipase C and receptor-operated Ca2+ channels that are regulated by PKC. Both PTX-sensitive and -insensitive guanine nucleotide-binding proteins appear to couple the PAF receptor to activation of phospholipase C and the increase in [Ca2+]i. These results contribute to the further understanding of the mechanisms behind PAF actions on neuronal cells.
Mol Pharmacol 1992 Feb
PMID:Platelet-activating factor stimulates phosphoinositide turnover in neurohybrid NCB-20 cells: involvement of pertussis toxin-sensitive guanine nucleotide-binding proteins and inhibition by protein kinase C. 131 8

We have previously shown that HeLa cells contain activities implicated in tRNA splicing in yeast, a ligase capable of joining tRNA half-molecules and an NAD-dependent activity capable of removing the 2'-phosphate created at the splice junction by the ligase (Zillmann, M., Gorovsky, M.A., and Phizicky, E.M. (1991) Mol. Cell. Biol. 11, 5410-5416). We show here that removal of the splice junction 2'-phosphate is, as in yeast, a 2'-phosphate-specific phosphotransfer reaction that produces the same, as yet unidentified, small molecule. This enzyme is highly specific for oligomeric substrates having internal 2'-phosphates. Oligomers bearing terminal 2'-phosphates are at least 50-fold less reactive and those bearing 5'- or 3'-terminal phosphates are at least 600-fold less reactive. The requirement for an internal 2'-phosphate can be satisfied by a substrate as small as a dimer.
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PMID:HeLa cells contain a 2'-phosphate-specific phosphotransferase similar to a yeast enzyme implicated in tRNA splicing. 131 96


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