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PubMed1980

[Effects of basic proteins of low molecular weight on the phosphohydrolase and phosphotransferase activities of microsomal glucose-6-phosphatase in adult monkey hepatocytes (author's transl)].

The effects of histone 2A and some polycations on microsomal carbamylphosphate:D-glucose phosphotransferase and glucose-6-phosphate phosphohydrolase activities (D-glucose-6-phosphate phosphohydrolase, EC 3.1.3.9), have been investigated. 1. Histone 2A and polycations activate the two enzymic activities. At a constant cation concentration, this activation increases with the number of cationic groups per molecule. 2. Activation by histone 2A is related to its fixation on microsomal membranes. This fixation varies with quantities of histones and pH. 3. The nature of the interactions between histones and microsomal membranes is shown to be electrostatic, probably between the cationic groups of histones and the anionic group of membranous lipids. 4. Kinetic analysis reveal that histone 2A increases the maximal reaction velocity but does not affect the apparent Michaelis constant values for the substrates. 5. The role played by the cationic groups of histone 2A on the microsomal glucose 6-phosphatase, is discussed.

Animals↗
PubMed1975

Comparative structural studies of the active site of ATP: guanidine phosphotransferases. The essential cysteine tryptic peptide of taurocyamine kinase from Arenicola marina.

The active cysteinyl residues of dimeric taurocyamine kinase from Arenicola marina were labelled with N-ethyl-[1-14C]maleimide. The resulting inactivated N-ethyl-[1-14C]succinimido enzyme was then subjected to tryptic hydrolysis. The peptide containing the labelled essential cysteinyl residue was isolated. The amino acid sequence of this peptide is Leu-Gly-Tyr-Leu-Gly-Thr-[14C]-Cys-Pro-Thr-Asn-Ile-Gly-Leu-Arg. This sequence is very similar to that of homologous ATP:guanidine phosphotransferases previously studied, arginine kinase from Homarus vulgaris muscle, creatine kinase from ox brain and ox muscle, and from rabbit muscle, and lombricine kinase from Lubricus terrestris.

Alkanesulfonates↗
PubMed1983

Molecular cloning and expression in streptomyces lividans of a hygromycin B phosphotransferase gene from Streptomyces hygroscopicus.

The gene encoding the phosphotransferase enzyme that modifies hygromycin B in its producing organism Streptomyces hygroscopicus, has been cloned in the Streptomyces vector pIJ41. Two plasmids, pFM4 and pFM6, containing 2.1 and 19.6 kb inserts of Streptomyces hygroscopicus DNA, respectively, which express the modifying enzyme, have been isolated. A 3.1 kb PstI restriction fragment from pFM4 was inserted in the Streptomyces vector pIJ350 and the resulting plasmids, pMZ11.1 and pMZ11.2, express the hygromycin B-resistance phenotype. The utility of this dominant marker for cloning experiments is discussed in the text.

Bacillus subtilis↗
PubMed1985

A source of apparent pyrophosphate:fructose 6-phosphate phosphotransferase activity in rabbit muscle phosphofructokinase.

In the presence of UDPglucose, rabbit muscle phosphofructokinase appeared to use PPi as a phosphoryl donor, as reported previously (Biochem. Biophys. Res. Commun. 121, 842-847). This apparent activity was due to conversion of UDPglucose and PPi to glucose 1-phosphate and UTP, the latter being metabolized by phosphofructokinase. Auxiliary enzymes used in the assays were contaminated by UDPglucose pyrophosphorylase. This contamination was sufficient to account for, and had similar properties to, the apparent PPi-dependent activity. Without auxiliary enzymes phosphofructokinase could not use PPi. These findings indicate that the apparent interconversion of phosphofructokinase and PPi:fructose 6-phosphate phosphotransferase must be re-assessed.

Animals↗
PubMed1987

Phosphorylation of the alpha 1,2-linked mannosylsaccharide by N-acetylglucosamine-1-phosphotransferase from fibroblasts occurs at the terminal mannose.

UDP-GlcNAc: Lysosomal enzyme precursor N-acetylglucosamine-1-phosphotransferase activity from normal fibroblasts was measured using methyl 2-O-(alpha-D-mannopyranosyl) 6-deoxy-6-fluoro-alpha-D-mannopyranoside and methyl 2-O-(6-deoxy-6-fluoro-alpha-D-mannopyranosyl) alpha-D-mannopyranoside as acceptors. The results indicate that the phosphorylation in man alpha 1----2 man sequence occurs at the C-6 position of the terminal mannose residue.

Fibroblasts↗
PubMed1991

The phosphotransferase activity of casein kinase II is required for its physiological function in vivo.

We have previously shown that the inviability associated with disruption of both catalytic subunits of casein kinase II in Saccharomyces cerevisiae can be rescued by plasmids expressing the catalytic subunit of the Drosophila enzyme (Padmanabha et al., 1990, Mol. Cell. Biol. 10, 4089). Here we describe the construction of mutant forms of the Drosophila catalytic subunit in which residues known to be crucial for catalytic activity in other protein kinases have been altered by site-directed mutagenesis. Mutation of either Lys66 or Asp173, which correspond to Lys72 and Asp184 of cAMP-dependent protein kinase, respectively, yields a casein kinase II catalytic subunit which fails to rescue a yeast strain lacking both endogenous catalytic subunit genes. The data indicate that the phosphotransferase activity of casein kinase II is required for its physiological function in vivo.

Animals↗
PubMed1992

Site-specific mutations of conserved C-terminal residues in aminoglycoside 3'-phosphotransferase II: phenotypic and structural analysis of mutant enzymes.

In order to test the biological importance of amino acids in the C-terminal quarter of aminoglycoside 3'-phosphotransferase II enzyme, seven of the highly conserved residues in this region, His-188, Asp-190, Asp-208, Gly-210, Arg-211, Asp-216 and Asp-220, were changed via site-directed mutagenesis. The phenotype of each mutant was compared to wildtype in terms of antibiotic susceptibilities and enzymatic activities. All of the substitutions either abolished or significantly reduced the resistance of the resulting strains to kanamycin, neomycin, butirosin, ribostamycin, paromomycin, gentamicin A, and G-418. Similarly, enzyme activities in crude extracts were substantially reduced for the mutant strains. Affinity of the enzyme for Mg+2-ATP decreased with His-188, Asp-190, Asp-216 and Asp-220 substitutions as revealed by Km measurements. Secondary structure analysis predicted that substitutions at the conserved residues caused severe conformational distortions at the corresponding regions of the protein.

Amino Acid Sequence↗
PubMed1989

Tritrichomonas foetus: purification and characterization of hydrogenosomal ATP:AMP phosphotransferase (adenylate kinase).

The hydrogenosomal enzyme ATP:AMP phosphotransferase (adenylate kinase) (EC 2.7.4.3) was purified to apparent homogeneity from the bovine parasite Tritrichomonas foetus. A fraction enriched for hydrogenosomes was obtained from cell homogenates which had been subjected to differential and isopycnic centrifugation. Adenylate kinase was solubilized in 50 mM Tris-HCl, pH 7.3, containing 0.8% Triton X-100, and purified by sequential Affi-Gel blue affinity chromatography and high-performance liquid chromatography gel filtration. The purified enzyme, a monomer of Mr 29,000, exhibited Km values of 100, 195, and 83 microM for ADP, ATP, and AMP, respectively. Substituting other mono-, di-, and trinucleotides for AMP, ADP, and ATP gave less than half the maximal activity. Full enzyme activity requires Mg2+, but Mn2+ and Co2+ yield half maximal activity. The enzyme has a broad optimal pH range between pH 6 and 9. The enzyme was competitively inhibited by P1,P5-di(adenosine-5')pentaphosphate, a specific adenylate kinase inhibitor: the Ki was 150 nM. The enzyme was also inhibited with 5,5'-dithiobis(2-nitrobenzoic acid), and this inhibition could be reversed by the addition of 2 mM dithiothreitol. T. foetus adenylate kinase has similar catalytic and physical properties to that of the biologically closely related human parasite Trichomonas vaginalis.

Adenylate Kinase↗
PubMed1986

The complete primary structure of GTP:AMP phosphotransferase from beef heart mitochondria.

To complete the amino acid sequence of GTP:AMP phosphotransferase (MgGTP + AMP in equilibrium with MgGDP + ADP) from beef heart mitochondria it was necessary to sequence an intermediate region of about 33 residues after position 102 [(1984) Eur. J. Biochem. 143, 331-339] and find a suitable overlap with the rest of the protein. The required peptides were obtained by cleaving the enzyme with endoproteinase Lys-C. One peptide, covering the region from residue 79 to 144, was sequenced up to residue 124. Another peptide, extending from residue 79 to 169, was subcleaved with Staphylococcus aureus V8 protease and provided the fragment from residue 99 to 139 which was sequenced. Several other peptides from endoproteinase Lys-C cleavage were used to check large sections of the previously published sequence work. The complete sequence contains 225 amino acids and has an Mr of 25 469.

Amino Acid Sequence↗
PubMed1987

Susceptibility of protein kinase C to oxidative inactivation: loss of both phosphotransferase activity and phorbol diester binding.

Exposure of protein kinase C to low concentrations of either N-chlorosuccinimide or H2O2 resulted in rapid and parallel loss of phosphotransferase activity and phorbol ester binding. This oxidative inactivation of protein kinase C also occurred in intact cells exposed to a low concentration of H2O2. With H2O2 treatment the rate of inactivation of protein kinase C in the cytosol of MCF-7 cells was rather slower than that which occurred in the cytosol of PYS cells. However, in both cell types, the oxidative inactivation of membrane-associated protein kinase C occurred rapidly in comparison to the enzyme in the cytosol. Prior treatment of cells with phorbol ester to induce membrane association (stabilization) of protein kinase C, followed by exposure to H2O2, resulted in increased inactivation of protein kinase C, suggesting that membrane association of protein kinase C increases its susceptibility to oxidative inactivation.

Animals↗
PubMed1993

Glycogen contains phosphodiester groups that can be introduced by UDPglucose: glycogen glucose 1-phosphotransferase.

Rabbit-muscle glycogen contains covalently bound phosphorus, equivalent to 1 phosphate group per 208 glucose residues. This often disputed, minor component was previously thought to represent a phosphomonoester group at C-6 of a glucose residue. Here we show that more than half the phosphorus is present as a phosphodiester, the remainder being monoester. A novel enzyme activity has been found in muscle that can account for the presence of the phosphodiester in glycogen. This is a UDPglucose: glycogen glucose 1-phosphotransferase that positions glucose 1-phosphate on C-6 of glucose residues in glycogen, forming a diester. The phosphomonoester groups present may arise by removal of the glucose residue originally transferred as glucose 1-phosphate.

Animals↗
PubMed1995

Investigation of transphosphorylation between chemotaxis proteins and the phosphoenolpyruvate:sugar phosphotransferase system.

Transphosphorylation between the chemotaxis proteins and phosphoenolpyruvate:sugar phosphotransferase system (PTS) from Escherichia coli was investigated by incubating the CheA, CheW and CheY proteins of the chemotaxis cascade, and Enzyme I, HPr and Enzyme IImtl of the PTS with [gamma-32P]ATP or [32P]phosphoenolpyruvate in the presence and absence of cell extract. In the absence of cell extract, ATP phosphorylated CheA, but in the presence of cell extract, Enzyme I was also phosphorylated. Phosphoenolpyruvate phosphorylated only PTS components. The transphosphorylation of Enzyme I by ATP did not require chemotaxis proteins, and likely occurred through acetate kinase. Regardless of phosphorylation state, the HPr protein did not inhibit the rate of ATP-dependent phosphorylation of the CheA or the CheY protein. It is concluded that chemotaxis to PTS substrates is not mediated by transphosphorylation between the PTS and chemotaxis systems.

Bacterial Proteins↗
PubMed1982

Characterization of six nucleoside-nucleotide phosphotransferases from the chromatin of Morris hepatoma 9121 cells by physicochemical and biochemical techniques.

1. Six nucleoside-nucleotide phosphotransferases A-F were isolated from chromatin of Morris Hepatoma 9121 cells and characterized. 2. The apparent mol wt are: 13,000 daltons for A, 35,000 or 70,000 for B and E, 240,000 for C, 180,000 for D and 300,000-400,000 for F. 3. The sedimentation values are: 2.5-3 S for A, 3 or 5 S for B and E, 11 S for C, 7-8 S for D and 14 S for F. 4. The activity of the six enzymes A-F was stimulated with 1-2.5 micrograms calf thymus DNA using thymidine/ATP as substrates. 5. In the presence of defined polydeoxynucleotides, each enzyme A-F showed a differential preference for its substrates.

Adenosine Triphosphate↗
PubMed1983

Synthesis of nucleotides by phosphotransferase from human tissues.

Several human tissues (prostate greater than liver greater than kidney greater than spleen) contain phosphotransferase capable of synthesizing nucleoside monophosphate by low-energy phosphate transfer to pyrimidines, purines as well as ribo- and deoxyribonucleosides. Phenyl phosphate, AMP, TMP, GMP and IMP were good phosphate donors while thymidine, deoxyadenosine and deoxyuridine are the most effectively utilized substrates. The phosphatransferase activity is present in all particulate fractions with most activity in microsomes. The enzyme is being purified from human tissues.

Adipose Tissue↗
PubMed1983

Allosteric effects of cortisol, estradiol, progesterone and of the DNA-sequences poly d(A-T) and poly d(C-G) on the adenosine and thymidine phosphorylating activity of the nuclear nucleoside-nucleotide phosphotransferase C.

The ATP-synthesis of the nuclear nucleoside-nucleotide phosphotransferase C was stimulated by progesterone alone and in combination with poly d(A-T) at 10(-10)-10(-9) M, by estradiol/poly d(A-T) at 5-10(-9) M, by cortisol alone and in combination with poly d(A-T) at 10(-9)-10(-8) M and by poly d(A-T) alone. No effect was observed using poly d(C-G). Using increasing adenosine/dTTP as substrates, cortisol, progesterone, estradiol/poly d(A-T) and poly d(A-T) alone caused positive cooperativity of the substrate saturation curves of the allosteric enzyme C by lowering the apparent Ks 0.5-values and by altering Vmax. The dTTP-synthesis of enzyme C was stimulated by both poly d(A-T) and poly d(C-G) alone and in combination with low estradiol (up to 10(-10) M)-and with higher progesterone concentrations (10(-8)-10(-7) M), whereas cortisol inhibited at higher concentrations completely. Using increasing thymidine/ATP as substrates progesterone and estradiol, also in combination with poly d(A-T) were positive effectors of the substrate saturation curves of enzyme C. By this, the apparent Ks 0.5-values or Vmax were changed. Cortisol could be shown to be a negative effector.

Adenosine↗
PubMed1984

Preliminary crystallographic data for a monoclonal Fab fragment specific for HPr of the phosphoenolpyruvate: sugar phosphotransferase system of Escherichia coli.

Crystals for Fab fragments from a monoclonal antibody to HPr of the phosphoenopyruvate:sugar phosphotransferase system of Escherichia coli have been obtained from 14% polyethylene glycol 6000, 5 mM-Tris X HCl, 50 mM-sodium phosphate and 0.2 M-sodium chloride at pH 8.0. The space group is P2(1) with a = 110.85 A, b = 66.18 A, c = 67.21 A, beta = 113.0 degrees and Z = 4. The crystals exhibit the forms [100], [011] and [011] and the solvent content is 47%.

Antibodies, Monoclonal↗
PubMed1982

A UDP-glucose:glycoprotein glucose-1-phosphotransferase in embryonic chicken neural retina.

A subclass of cell-surface glycoproteins from embryonic chicken neural retina contains a high mannose-type oligosaccharide that terminates with glucose linked via a phosphodiester bond to penultimate mannose. This unusual oligosaccharide seems responsible for the glycoprotein attachments to the cell-surface baseplate ligatin. Using beta-32P-UDP-3H-glucose, we demonstrate in retinal homogenates the existence of a UDP-glucose:glycoprotein glucose-1-phosphotransferase (GlcPTase) that catalyzes the synthesis of such a linkage. Characterization of the doubly labeled product resulting from activity of the transferase reveals a family of endoglycosidase H-sensitive oligosaccharides displaying a cation-exchange profile similar to that of oligosaccharides derived from ligatin-associated proteins synthesized in vivo. Further analysis confirms that the incorporation of label is due to a terminal 3H-glucose joined via a 32P-phosphodiester linkage to carbon 6 of a penultimate mannose. We propose that GlcPTase may be a controlling enzyme for the targeting of certain newly synthesized proteins to the cell surface.

Animals↗