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

2-Deoxy-D-galactose, in a dose of 3 mmol/kg, was administered intraperitoneally twice daily to young rats for periods up to 12 weeks. This dosage schedule resulted in recurrent phosphate trapping predominantly in liver. UTP deficiency was excluded by simultaneous uridine injections. Phosphate trapping was caused by the rapid accumulation of 2-deoxy-D-galactose 1-phosphate and was most pronounced in liver but also demonstrated in small intestine, brain, spleen, and thymus. The marked, although transient, drop in the hepatic content of inorganic phosphate triggered the catabolism of adenine nucleotides and a loss of ATP. Other metabolic pathways affected by phosphate deficiency include glycogenolysis and glycolysis. Increasing with time, repeated doses of the galactose analog led to retardation and arrest of growth, hepatomegaly, and splenomegaly. The average relative liver and spleen weights were elevated 2.5- and 4.5-fold, respectively, after 12 weeks of treatment. Liver damage was indicated by hyperbilirubinaemia and a progressive rise in the activity in plasma of sorbitol dehydrogenase, alkaline phosphatase, and gamma-glutamyltransferase. Examination by light and electron microscopy showed increasing numbers of vacuoles, surrounded by a single membrane, in hepatocytes, sinusoidal endothelial cells, and Kupffer cells. Focal cytoplasmic degeneration in hepatocytes was occasionally indicated by formation of autophagic vacuoles and finger print lysosomes. Hepatocytes of 2-deoxy-D-galactose-treated rats showed a dissociation and fragmentation of the rough endoplasmic reticulum. Sinusoidal endothelial cells and Kupffer cells were markedly enlarged, the latter contained a PAS-positive but amylase resistant substance. Extrahepatic changes included an increased occurrence of vacuolated cells in thymus. Phosphate trapping and its metabolic consequences are common phenomena in the experimental injury induced b 2-deoxy-D-galactose and in some hereditary diseases such as uridylyltransferase deficiency galactosaemia, fructose intolerance and glucose-6-phosphatase deficiency.
Virchows Arch B Cell Pathol Incl Mol Pathol 1979 Jun 29
PMID:Consequences of recurrent phosphate trapping induced by repeated injections of 2-deoxy-D-galactose. Biochemical and morphological studies in rats. 4 10

Histochemical observations were made of the activities of nucleosidephosphatases splitting ATP, ADP, IDP, and AMP and exopeptidases splitting l-alanine, l-leucine and l-glycyl-proline in the spleen sinuses of man, mouse, rat, hamster, and rabbit. Of the exopeptidases, only glycylprolyl-naphthylamidase could be proved histochemically, and that only in man and rat. Nucleosidephosphatases showed only traces of activity except in the rabbit where there was highly active AMP-ase, the others being moderately active.
Virchows Arch B Cell Pathol Incl Mol Pathol 1979 Dec
PMID:Comments on spleen sinus enzyme equipment. A histochemical study. 4 57

The interaction between beef pancreas tryptophanyl-tRNA synthetase and its fragments produced after limited proteolysis, with IgG fraction of antiserum and with Fab fragment of IgG has been studied. Both the intact antibodies and Fab fragments inhibit the enzyme activity in tRNA aminoacylation and tryptophan dependent ATP-32P pyrophosphate exchange reactions. However, the enzyme inhibited by antibodies is still able to form a complex with tryptophanyl-tRNA. The enzymatically active fragment obtained after endogenous proteolysis interacts only with 1/3 of the antibodies against native enzyme. The fragment produced by trypsinolysis possess similar immunochemical properties. This fragment has almost the same molecular weight but is enzymatically inactive. Pure antibodies against tryptic fragment isolated by means of specific immunoabsorbent inhibit the enzymatic activity. The antibodies which do not interact with this fragment (2/3 of the total amount of antibodies) have no influence on the enzymatic activity. The immunochemical identity of the two synthetase fragments differing in their enzymatic activity supports the assumption that the loss of enzymatic activity of the tryptis fragment is caused by lack of a small peptide which is retained in case of endogenous proteolysis. Probably the amino acid residues of this peptide participate in formation of the active centre of tryptophanyl-tRNA synthetase. A new procedure for determination of the number of antigenic determinants in proteins is developed. It is shown by this method that beef pancreas tryptophanyl-tRNA synthetase contains 9 +/- 1 antigenic determinants.
Mol Biol (Mosk)
PMID:[Immunochemical properties of tryptophanyl-tRNA synthetase and its fragments]. 8 56

The fraction inhibiting ATP-dependent DNAase and some other enzyme activities was found in B. subtilis cell extracts. Two methods of its isolation were elaborated. It is established that the inhibiting activity fraction represents a set of some positively charged thermostable proteins of low molecular weight (M 9000--25 000). The inhibiting effect of the proteins in question may be attributed to their ability to form a complex with DNA. The complex is formed in low ionic strength conditions. The elevation of NaCl concentration to 0,3 M removes some proteins from the complex and causes the complete loss of inhibiting activity. At 0,5 M NaCl DNA-protein complex is completely dissociated. The discovered proteins seems to be localized in DNA-membrane cell fraction. It is supposed that these proteins (or some of them) are the structural ones of the bacterial nucleoid.
Mol Biol (Mosk)
PMID:[Isolation and properties of B. subtilis DNA-binding proteins inhibiting ATP-dependent deoxyribonuclease]. 11 Oct 35

Basal and trypsin-stimulated adenosine triphosphatase activities of Escherichia coli K 12 have been characterized at pH 7.5 in the membrane-bound state and in a soluble form of the enzyme. The saturation curve for Mg2+/ATP = 1/2 was hyperbolic with the membrane-bound enzyme and sigmoidal with the soluble enzyme. Trypsin did not modify the shape of the curves. The kinetic parameters were for the membrane-bound ATPase: apparent Km = 2.5 mM, Vmax (minus trypsin) = 1.6 mumol-min-1-mg protein-1, Vmax (plus trypsin) = 2.44 mumol-min-1-mg protein-1; for the soluble ATPase: [S0.5] = 1.2 mM, Vmax (-trypsin) = 4 mumol-min-1-mg protein-1; Vmax (+ trypsin) = 6.6 mumol-min-1-mg protein-1. Hill plot analysis showed a single slope for the membrane-bound ATPase (n = 0.92) but two slopes were obtained for the soluble enzyme (n = 0.98 and 1.87). It may suggest the existence of an initial positive cooperativity at low substrate concentrations followed by a lack of cooperativity at high ATP concentrations. Excess of free ATP and Mg2+ inhibited the ATPase but excess of Mg/ATP (1/2) did not. Saturation for ATP at constant Mg2+ concentration (4 mM) showed two sites (groups) with different Kms: at low ATP the values were 0.38 and 1.4 mM for the membrane-bound and soluble enzyme; at high ATP concentrations they were 17 and 20 mM, respectively. Mg2+ saturation at constant ATP (8 mM) revealed michealian kinetics for the membrane-bound ATPase and sigmoid one for the protein in soluble state. When the ATPase was assayed in presence of trypsin we obtained higher Km values for Mg2+. These results might suggest that trypsin stimulates E. coli ATPase by acting on some site(s) involved in Mg2+ binding. Adenosine diphosphate and inorganic phosphate (Pi) act as competitive inhibitors of Escherichia coli ATPase. The Ki values for Pi were 1.6 +/- 0.1 mM for the membrane-bound ATPase and 1.3 +/- 0.1 mM for the enzyme in soluble form, the Ki values for ADP being 1.7 mM and 0.75 mM for the membrane-bound and soluble ATPase, respectively. Hill plots of the activity of the soluble enzyme in presence of ADP showed that ADP decreased the interaction coefficient at ATP concentrations below its Km value. Trypsin did not modify the mechanism of inhibition or the inhibition constants. Dicyclohexylcarbodiimide (0.4 mM) inhibited the membrane-bound enzyme by 60-70% but concentrations 100 times higher did not affect the residual activity nor the soluble ATPase. This inhibition was independent of trypsin. Sodium azide (20 muM) inhibited both states of E. coli ATPase by 50%. Concentrations 25-fold higher were required for complete inhibition. Ouabain, atebrin and oligomycin did not affect the bacterial ATPase.
Mol Cell Biochem 1975 Nov 14
PMID:Membrane bound and soluble adenosine triphosphatase of Escherichia coli K 12. Kinetic properties of the basal and trypsin-stimulated activities. 12 30

Two new forms of the plasma membrane ATP-ase of Micrococcus lysodeikticus NCTC 2665 were isolated from a sub-strain of the microorganism by polyacrylamide gel electrophoresis. One of them had a mol.wt of 368,000 and a very low specific activity (0.80 mumol.min-1.mg protein-1) that could not be stimulated by trypsin. This form has been called B1 (strain B, inactive). If the elctrophoresis was carried out in the presence of reducing agents (i.e., dithiothreitol) and the pH of the effluent maintained at a value of 8.5 another form of the enzyme was obtained. This had a mol.wt of 385,000 and a specific activity of 2.5-5.0 mumol.min-1.mg protein-1 that could be stimulated by trypsin to 5-10 mumol.min-1.mg protein-1. This preparation of the ATPase has been called from BA (strain B, enzyme active). The subunit composition of both forms has been studied by sodium dodecyl sulphate and urea gel electrophoresis and compared to that of the enzyme previously purified from the original strain (form A). The three forms of the enzyme had similar beta and delta subunits, with mol.wt of about 50,000 and 30,000 dalton, respectively. They also had in common the component(s) of relative mobility 1.0, whose status as true subunit(s) of the enzyme remains yet to be established. However, subunit alpha, that had a mol.wt of about a 52,500 in form A (ANDREU et al. Eur. J. Biochem. (1973) 37, 505-515), had a mol.wt similar to beta in form B1 and about 60,000 in form BA. Furthermore BA usually showed two types of this subunit (alpha' and alpha") and an additional peptide chain E) with a mol.wt of about 25,000 dalton. This latter subunit seemed to account for the stimulation by trypsin of form BA. Forms BA could be converted to B1 by storage and freezing and thawing. Conventional protease activity could not be detected in any of the purified ATPase forms and addition of protease inhibitors to form BA failed to prevent its conversion to form B1. The low activity form (B1) was more stable than the active forms of the enzyme and also differeed in its circular dichroism. These results show that M. lysodeikticus ATPase can be isolated in several forms. Although these variations may be artifacts caused by the purification procedures, they provide model systems for understanding the structural and functional relationships of the enzyme and for drawing some speculations about its function in vivo.
Mol Cell Biochem 1976 Feb 16
PMID:Membrane adenosine triphosphatase of Micrococcus lysodeikticus. ISolation of two forms of the enzyme complex and correlation between ezymatic stability, latency and activity. 13 May 38

Comparisons of the amino acid compositions of the nitrogenase proteins from different organisms and their correlation with cross-reactivities and taxonomical data suggest an evolution within bacterial genomes rather than within plasmids. Comparisons of the amino acid compositions of nitrogenases and other ATP-ases show similarities which might be due to the evolution of these ATP-ases from a common ancestral protein.
J Mol Evol 1976 Mar 29
PMID:Possible evolutionary relationships of the nitrogenase proteins. 13 Dec

1. The distribution of ATPase and several marker enzymes was examined after differential and sucrose gradient centrifugation of yeast homogenates. 2. An ATPase activity not sensitive to oligomycin is found exclusively associated with a particulate fraction equilibrating at densities of 1.23-1.25. This particulate material shows the chemical and enzymatic characteristics of the yeast plasma membrane. 3. The pH optimum of the plasma membrane ATPase is 5.6, as compared with 8.5 for the mitochondrial ATPase. In addition to oligomycin, the enzyme is not sensitive to other inhibitors of the mitochondrial ATPase as azide, dicyclohexylcarbodiimide and the mitochondrial ATPase inhibitor protein. It is inhibited by p-chloromercuryphenyl sulfonate, fluoride, quercetin and by the antibiotic Dio-9 but is not affected by ouabain. 4. The plasma membrane ATPase shows a high affinity for ATP (Km = 0.1 mM) and is very specific for this compound, hydrolyzing other nucleotide triphosphates less than 25% as rapidly. No activity was detected with ADP. 5. The enzyme requires a divalent cation for activity and Mg2+ is the most effective. It is not significantly stimulated by K+ or bicarbonate and Ca2+ is inhibitory. 6. The activity cannot be assayed in intact cells unless they are permeabilized with toluene. This suggest that the active site is on the cytoplasmic side of the plasma membrane.
Mol Cell Biochem 1978 Nov 30
PMID:Characterization of the plasma membrane ATPase of Saccharomyces cerevisiae. 15 59

Literature data and the author's materials concerning the intermediate stages of ATP hydrolysis by myosin and actomyosin are reviewed. The scheme of hydrolytic stages based on the application of fluorescent and UV spectroscopic stop-flow and 18O exchange methods is discussed. Some unsolved problems of the hydrolytic mechanism and its relation to energy transduction in the mechanochemical act are also considered.
Mol Biol (Mosk)
PMID:[Modern views on mechanism of ATP hydrolysis by myosin (on the 40th anniversary of myosin enzymatic activity discovery)]. 15 79

Considerable progress has been made in recent years in our understanding of the phosphorylating apparatus in mitochondria, chloroplasts, and bacteria. It has become clear that the structure and the function of the ATP synthesizing apparatus in these widely divergent organisms is similar if not virtually identical. The subunit composition of F1, its molecular architecture, the location and function of substrate binding sites, as well as putative control sites, understanding of the component parts of the oligomycin-sensitive ATPase complex, and the role of these components in the function of the complex all are under active investigation in many laboratories. The developing information and the new insights provided have begun to permit experimental approaches, at the molecular level, to the mode of action of the ATPase in electron-transport-coupled ATP synthesis.
Adv Enzymol Relat Areas Mol Biol 1979
PMID:Mitochondrial ATPase. 16 56


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