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The Journal of Biological Chemistry Oct 2007A novel sialyltransferase, alpha/beta-galactoside alpha-2,3-sialyltransferase, was purified from the cell lysate of a luminous marine bacterium, Photobacterium...
A novel sialyltransferase, alpha/beta-galactoside alpha-2,3-sialyltransferase, was purified from the cell lysate of a luminous marine bacterium, Photobacterium phosphoreum JT-ISH-467, isolated from the Japanese common squid (Todarodes pacificus). The gene encoding the enzyme was cloned from the genomic library of the bacterium using probes derived from the NH(2)-terminal and internal amino acid sequences. An open reading frame of 409 amino acids was identified, and the sequence had 32% identity with that of beta-galactoside alpha-2,6-sialyltrasferase in Photobacterium damselae JT0160. DNA fragments that encoded the full-length protein and a protein that lacked the sequence between the 2nd and 24th residues at the NH(2) terminus were amplified by polymerase chain reactions and cloned into an expression vector. The full-length and truncated proteins were expressed in Escherichia coli, producing active enzymes of 0.25 and 305 milliunits, respectively, per milliliter of the medium in the lysate of E. coli. The truncated enzyme was much more soluble without detergent than the full-length enzyme. The enzyme catalyzed the transfer of N-acetylneuraminic acid from CMP-N-acetylneuraminic acid to disaccharides, such as lactose and N-acetyllactosamine, with low apparent K(m) and to monosaccharides, such as alpha-methyl-galactopyranoside and beta-methyl-galactopyranoside, with much lower apparent K(m). Thus, this sialyltransferase is unique and should be very useful for achieving high productivity in E. coli with a wide substrate range.
Topics: Animals; Cloning, Molecular; Decapodiformes; Disaccharides; Galactose; Gene Expression Regulation, Enzymologic; Kinetics; Models, Biological; Molecular Sequence Data; N-Acetylneuraminic Acid; Photobacterium; Protein Structure, Tertiary; Sialic Acids; Sialyltransferases; Substrate Specificity; beta-Galactoside alpha-2,3-Sialyltransferase
PubMed: 17702755
DOI: 10.1074/jbc.M701907200 -
The New England Journal of Medicine Nov 2004Term infants who are small for gestational age appear prone to the development of insulin resistance during childhood. We hypothesized that insulin resistance, a marker...
BACKGROUND
Term infants who are small for gestational age appear prone to the development of insulin resistance during childhood. We hypothesized that insulin resistance, a marker of type 2 diabetes mellitus, would be prevalent among children who had been born prematurely, irrespective of whether they were appropriate for gestational age or small for gestational age.
METHODS
Seventy-two healthy prepubertal children 4 to 10 years of age were studied: 50 who had been born prematurely (32 weeks' gestation or less), including 38 with a birth weight that was appropriate for gestational age (above the 10th percentile) and 12 with a birth weight that was low (i.e., who were small) for gestational age, and 22 control subjects (at least 37 weeks' gestation, with a birth weight above the 10th percentile). Insulin sensitivity was measured with the use of paired insulin and glucose data obtained by frequent measurements during intravenous glucose-tolerance tests.
RESULTS
Children who had been born prematurely, whether their weight was appropriate or low for gestational age, had an isolated reduction in insulin sensitivity as compared with controls (appropriate-for-gestational-age group, 14.2x10(-4) per minute per milliunit per liter [95 percent confidence interval, 11.5 to 16.2]; small-for-gestational-age group, 12.9x10(-4) per minute per milliunit per liter [95 percent confidence interval, 9.7 to 17.4]; and control group, 21.6x10(-4) per minute per milliunit per liter [95 percent confidence interval, 17.1 to 27.4]; P=0.002). There were no significant differences in insulin sensitivity between the two premature groups (P=0.80). As compared with controls, both groups of premature children had a compensatory increase in acute insulin release (appropriate-for-gestational-age group, 2002 pmol per liter [95 percent confidence interval, 1434 to 2432] [corrected]; small-for-gestational-age group, 2253 pmol per liter [95 percent confidence interval, 1622 to 3128]; and control group, 1148 pmol per liter [95 percent confidence interval, 875 to 1500]; P<0.001).
CONCLUSIONS
Like children who were born at term but who were small for gestational age, children who were born prematurely have an isolated reduction in insulin sensitivity, which may be a risk factor for type 2 diabetes mellitus.
Topics: Blood Glucose; Child; Child, Preschool; Diabetes Mellitus, Type 2; Female; Follow-Up Studies; Glucose Tolerance Test; Humans; Infant, Low Birth Weight; Infant, Newborn; Infant, Premature; Infant, Small for Gestational Age; Insulin Resistance; Linear Models; Male; Risk Factors
PubMed: 15548778
DOI: 10.1056/NEJMoa042275 -
Proceedings of the National Academy of... May 2004Genetic analysis indicates that Escherichia coli possesses two independent pathways for oxidation of phosphite (Pt) to phosphate. One pathway depends on the 14-gene phn...
Genetic analysis indicates that Escherichia coli possesses two independent pathways for oxidation of phosphite (Pt) to phosphate. One pathway depends on the 14-gene phn operon, which encodes the enzyme C-P lyase. The other pathway depends on the phoA locus, which encodes bacterial alkaline phosphatase (BAP). Transposon mutagenesis studies strongly suggest that BAP is the only enzyme involved in the phoA-dependent pathway. This conclusion is supported by purification and biochemical characterization of the Pt-oxidizing enzyme, which was proven to be BAP by N terminus protein sequencing. Highly purified BAP catalyzed Pt oxidation with specific activities of 62-242 milliunits/mg and phosphate ester hydrolysis with specific activities of 41-61 units/mg. Surprisingly, BAP catalyzes the oxidation of Pt to phosphate and molecular H2. Thus, BAP is a unique Pt-dependent, H2-evolving hydrogenase. This reaction is unprecedented in both P and H biochemistry, and it is likely to involve direct transfer of hydride from the substrate to water-derived protons.
Topics: Alkaline Phosphatase; Escherichia coli; Hydrogen; Hydrogenase; Hydrolysis; Mutation; Oxidation-Reduction; Phosphates; Phosphites; Protons
PubMed: 15148399
DOI: 10.1073/pnas.0400664101 -
Proceedings of the National Academy of... Jun 2003Mitochondria are the primary site of skeletal muscle fuel metabolism and ATP production. Although insulin is a major regulator of fuel metabolism, its effect on...
Mitochondria are the primary site of skeletal muscle fuel metabolism and ATP production. Although insulin is a major regulator of fuel metabolism, its effect on mitochondrial ATP production is not known. Here we report increases in vastus lateralis muscle mitochondrial ATP production capacity (32-42%) in healthy humans (P < 0.01) i.v. infused with insulin (1.5 milliunits/kg of fat-free mass per min) while clamping glucose, amino acids, glucagon, and growth hormone. Increased ATP production occurred in association with increased mRNA levels from both mitochondrial (NADH dehydrogenase subunit IV) and nuclear [cytochrome c oxidase (COX) subunit IV] genes (164-180%) encoding mitochondrial proteins (P < 0.05). In addition, muscle mitochondrial protein synthesis, and COX and citrate synthase enzyme activities were increased by insulin (P < 0.05). Further studies demonstrated no effect of low to high insulin levels on muscle mitochondrial ATP production for people with type 2 diabetes mellitus, whereas matched nondiabetic controls increased 16-26% (P < 0.02) when four different substrate combinations were used. In conclusion, insulin stimulates mitochondrial oxidative phosphorylation in skeletal muscle along with synthesis of gene transcripts and mitochondrial protein in human subjects. Skeletal muscle of type 2 diabetic patients has a reduced capacity to increase ATP production with high insulin levels.
Topics: Adenosine Triphosphate; Adult; Cell Nucleus; Citrate (si)-Synthase; DNA, Complementary; Diabetes Mellitus, Type 2; Dose-Response Relationship, Drug; Electron Transport Complex IV; Female; Glucose Tolerance Test; Humans; Insulin; Male; Mitochondria; Muscle, Skeletal; Oxygen; Protein Biosynthesis; RNA; RNA, Messenger; Reverse Transcriptase Polymerase Chain Reaction; Substrate Specificity; Time Factors
PubMed: 12808136
DOI: 10.1073/pnas.1332551100 -
The Journal of Biological Chemistry Nov 2002The 3-hydroxyacyl ACP:CoA transacylase (PhaG) was recently identified in various Pseudomonas species and catalyzes the diversion of ACP thioester intermediates of fatty... (Comparative Study)
Comparative Study
The 3-hydroxyacyl ACP:CoA transacylase (PhaG) was recently identified in various Pseudomonas species and catalyzes the diversion of ACP thioester intermediates of fatty acid de novo biosynthesis toward the respective CoA thioesters, which serve as precursors for polyester and rhamnolipid biosynthesis. PhaG from Pseudomonas putida was overproduced in Escherichia coli as a C-terminal hexahistidine-tagged (His(6)) fusion protein in high yield. The His(6)-PhaG was purified to homogeneity by refolding of PhaG obtained from inclusion bodies, and a new enzyme assay was established. Kinetic analysis of the 3-hydroxyacyl transfer to ACP, catalyzed by His(6)-PhaG, gave K(0.5) values of 28 microm (ACP) and 65 microm (3-hydroxyacyl-CoA) considering V(max) values of 11.7 milliunits/mg and 12.4 milliunits/mg, respectively. A Hill coefficient of 1.38 (ACP) and 1.32 (3-hydroxyacyl-CoA) indicated a positive substrate cooperativity. Subcellular localization studies showed that PhaG is not attached to polyester granules and resides in the cytosol. Gel filtration chromatography analysis in combination with light scattering analysis indicated substrate-induced dimerization of the transacylase. A threading model of PhaG was developed based on the homology to an epoxide hydrolase (1cqz). In addition, the alignment with the alpha/beta-hydrolase fold region indicated that PhaG belongs to alpha/beta-hydrolase superfamily. Accordingly, CD analysis suggested a secondary structure composition of 29% alpha-helix, 22% beta-sheet, 18% beta-turn, and 31% random coil. Site-specific mutagenesis of seven highly conserved amino acid residues (Asp-60, Ser-102, His-177, Asp-182, His-192, Asp-223, His-251) was used to validate the protein model and to investigate organization of the transacylase active site. Only the D182(A/E) mutation was permissive with about 30% specific activity of the wild type enzyme. Furthermore, this mutation caused a change in substrate specificity, indicating a functional role in substrate binding. The serine-specific agent phenylmethylsulfonyl fluoride (PMSF) or the histidine-specific agent diethylpyrocarbonate (DEPC) caused inhibition of 3-hydroxyacyl transfer to holo-ACP, and the S102(A/T) or H251(A/R) PhaG mutant was incapable of catalyzing 3-hydroxyacyl transfer, suggesting that these residues are part of a catalytic triad.
Topics: Acyltransferases; Amino Acid Sequence; Amino Acid Substitution; Animals; Chromatography, Gel; Circular Dichroism; Epoxide Hydrolases; Fatty Acids; Kinetics; Mice; Molecular Sequence Data; Mutagenesis, Site-Directed; Protein Conformation; Pseudomonas putida; Recombinant Proteins; Sequence Alignment; Subcellular Fractions
PubMed: 12200450
DOI: 10.1074/jbc.M207821200 -
The Journal of Biological Chemistry Jun 2002We have investigated the ability of a receptor-mediated gene transfer strategy (cross-correction) to restore ganglioside metabolism in fibroblasts from Tay-Sachs (TS)...
We have investigated the ability of a receptor-mediated gene transfer strategy (cross-correction) to restore ganglioside metabolism in fibroblasts from Tay-Sachs (TS) patients in vitro. TS disease is a GM2 gangliosidosis attributed to the deficiency of the lysosomal enzyme beta-hexosaminidase A (HexA) (beta-N-acetylhexosaminidase, EC ). The hypothesis is that transduced cells overexpressing and secreting large amounts of the enzyme would lead to a measurable activity in defective cells via a secretion-recapture mechanism. We transduced NIH3T3 murine fibroblasts with the LalphaHexTN retroviral vector carrying the cDNA encoding for the human Hex alpha-subunit. The Hex activity in the medium from transduced cells was approximately 10-fold higher (up to 75 milliunits) than observed in non-transduced cells. TS cells were cultured for 72 h in the presence of the cell medium derived from the transduced NIH3T3 cells, and they were analyzed for the presence and catalytic activity of the enzyme. Although TS cells were able to efficiently uptake a large amount of the soluble enzyme, the enzyme failed to reach the lysosomes in a sufficient quantity to hydrolyze the GM2 ganglioside to GM3 ganglioside. Thus, our results showed that delivery of the therapeutic HexA was not sufficient to correct the phenotype of TS cells.
Topics: 3T3 Cells; Animals; Cells, Cultured; DNA, Complementary; G(M2) Ganglioside; Gene Transfer Techniques; Genetic Vectors; Humans; Hydrolysis; Mice; Retroviridae; Tay-Sachs Disease
PubMed: 11923278
DOI: 10.1074/jbc.M106164200 -
The Journal of Biological Chemistry Apr 2002Based on the previous report of McCord and co-workers (Crow, J. P., Beckman, J. S., and McCord, J. M. (1995) Biochemistry 34, 3544-3552), the zinc dithiolate active site...
Based on the previous report of McCord and co-workers (Crow, J. P., Beckman, J. S., and McCord, J. M. (1995) Biochemistry 34, 3544-3552), the zinc dithiolate active site of alcohol dehydrogenase (ADH) has been studied as a target for cellular oxidants. In the nitrogen monoxide ((*NO)/superoxide (O(2)) system, an equimolar generation of both radicals under peroxynitrite (PN) formation led to rapid inactivation of ADH activity, whereas hydrogen peroxide and ( small middle dot)NO alone reacted too slowly to be of physiological significance. 3-Morpholino sydnonimine inactivated the enzyme with an IC(50) value of 250 nm; the corresponding values for PN, hydrogen peroxide, and (*NO) were 500 nm, 50 microm, and 200 microm. When superoxide was generated at low fluxes by xanthine oxidase, it was quite effective in ADH inactivation (IC(50) (XO) approximately 1 milliunit/ml). All inactivations were accompanied by zinc release and disulfide formation, although no strict correlation was observed. From the two zinc thiolate centers, only the zinc Cys(2)His center released the metal by oxidants. The zinc Cys(4) center was also oxidized, but no second zinc atom could be found with 4-(2-pyridylazo)resorcinol (PAR) as a chelating agent except under denaturing conditions. Surprisingly, the oxidative actions of PN were abolished by a 2-3-fold excess of (*)NO under generation of a nitrosating species, probably dinitrogen trioxide. We conclude that in cellular systems, low fluxes of (*)NO and O(2) generate peroxynitrite at levels effective for zinc thiolate oxidations, facilitated by the nucleophilic nature of the complexed thiolate group. With an excess of (*)NO, the PN actions are blocked, which may explain the antioxidant properties of (*)NO and the mechanism of cellular S-nitrosations.
Topics: Animals; Biochemical Phenomena; Biochemistry; Cattle; Chelating Agents; Chromatography, High Pressure Liquid; Chromogenic Compounds; Disulfides; Dose-Response Relationship, Drug; Free Radicals; Hydrazines; Hydrogen Peroxide; Models, Chemical; Molsidomine; Nitric Oxide; Nitric Oxide Donors; Nitrogen; Nitrogen Oxides; Oxygen; Peroxynitrous Acid; Protein Binding; Resorcinols; Spectrophotometry; Spectrum Analysis, Raman; Spermine; Sulfhydryl Compounds; Superoxides; Time Factors; Ultraviolet Rays; Xanthine Oxidase; Zinc
PubMed: 11805115
DOI: 10.1074/jbc.M111988200 -
Proceedings of the National Academy of... Sep 2001Oral immunogenicity of recombinant hepatitis B surface antigen (HBsAg) derived from yeast (purified product) or in transgenic potatoes (uncooked unprocessed sample) was...
Oral immunogenicity of recombinant hepatitis B surface antigen (HBsAg) derived from yeast (purified product) or in transgenic potatoes (uncooked unprocessed sample) was compared. An oral adjuvant, cholera toxin, was used to increase immune responses. Transgenic plant material containing HBsAg was the superior means of both inducing a primary immune response and priming the mice to respond to a subsequent parenteral injection of HBsAg. Electron microscopy of transgenic plant samples revealed evidence that the HBsAg accumulated intracellularly; we conclude that natural bioencapsulation of the antigen may provide protection from degradation in the digestive tract until plant cell degradation occurs near an immune effector site in the gut. The correlate of protection from hepatitis B virus infection is serum antibody titers induced by vaccination; the protective level in humans is 10 milliunits/ml or greater. Mice fed HBsAg-transgenic potatoes produced HBsAg-specific serum antibodies that exceeded the protective level and, on parenteral boosting, generated a strong long-lasting secondary antibody response. We have also shown the effectiveness of oral delivery by using a parenteral prime-oral boost immunization schedule. The demonstrated success of oral immunization for hepatitis B virus with an "edible vaccine" provides a strategy for contributing a means to achieve global immunization for hepatitis B prevention and eradication.
Topics: Animals; Genetic Vectors; Hepatitis B; Hepatitis B Surface Antigens; Mice; Plants, Genetically Modified; Plasmids; Solanum tuberosum
PubMed: 11553782
DOI: 10.1073/pnas.191617598 -
The Journal of Biological Chemistry Oct 2001The genes coding for two different proteins with homologies to glutaredoxins have been identified in the genome of the malarial parasite Plasmodium falciparum. Both...
The genes coding for two different proteins with homologies to glutaredoxins have been identified in the genome of the malarial parasite Plasmodium falciparum. Both genes were amplified from a gametocytic cDNA and overexpressed in Escherichia coli. The smaller protein (named PfGrx-1) with 12.4 kDa in size exhibits the typical glutaredoxin active site motif "CPYC," shows glutathione-dependent glutaredoxin activity in the beta-hydroxyethyl disulfide (HEDS) assay, and reduces Trypanosoma brucei ribonucleotide reductase. Glutathione:HEDS transhydrogenase activity (approximately 60 milliunits/mg of protein) was clearly detectable in trophozoite extracts from eight different P. falciparum strains and did not differ between chloroquine-resistant and -sensitive parasites. Five different antimalarial drugs at 100 microm did not significantly influence isolated PfGrx-1 activity. In contrast, the second protein (deduced mass 19.9 kDa) with homology to glutaredoxins (31% identity to Schizosaccharomyces pombe in a 140-amino acid overlap) was not active in the HEDS assay; however, its general dithiol reducing activity was demonstrated in the insulin assay in the presence of dithiothreitol. Interestingly, the sequence contains a PICOT (for protein kinase C-interacting cousin of thioredoxin) homology domain, which might suggest regulatory functions of the protein. We named this protein PfGLP-1, for P. falciparum 1-Cys-glutaredoxin-like protein-1. In contrast to glutaredoxins, PfGLP-1 could not be reduced by glutathione. This is the first report on glutaredoxin-like proteins in the family of Plasmodia.
Topics: Amino Acid Sequence; Animals; Base Sequence; Carrier Proteins; Cloning, Molecular; DNA, Protozoan; Glutaredoxins; Insulin; Molecular Sequence Data; Oxidoreductases; Plasmodium falciparum; Protein Structure, Tertiary; Proteins; Protozoan Proteins; Recombinant Proteins; Ribonucleotide Reductases; Sequence Homology, Amino Acid
PubMed: 11479312
DOI: 10.1074/jbc.M105524200 -
The Journal of Biological Chemistry Jun 2001Muscles and fat cells develop insulin resistance when exposed to high concentrations of glucose and insulin. We used an isolated muscle preparation incubated with high...
Muscles and fat cells develop insulin resistance when exposed to high concentrations of glucose and insulin. We used an isolated muscle preparation incubated with high levels of glucose and insulin to further evaluate how glucose-induced insulin resistance (GIIR) is mediated. Incubation with 2 milliunits/ml insulin and 36 mm glucose for 5 h resulted in an approximately 50% decrease in insulin-stimulated muscle glucose transport. The decrease in insulin responsiveness of glucose transport induced by glucose was not due to impaired insulin signaling, as insulin-stimulated phosphatidylinositol 3-kinase activity and protein kinase B phosphorylation were not reduced. It has been hypothesized that entry of glucose into the hexosamine biosynthetic pathway with accumulation of UDP-N-acetylhexosamines (UDP-HexNAcs) mediates GIIR. However, inhibition of the rate-limiting enzyme GFAT (glutamine:fructose-6-phosphate amidotransferase) did not protect against GIIR despite a marked reduction of UDP-HexNAcs. The mRNA synthesis inhibitor actinomycin D and the protein synthesis inhibitor cycloheximide both completely protected against GIIR despite the massive increases in UDP-HexNAcs and glycogen that resulted from increased glucose entry. Activation of AMP-activated protein kinase also protected against GIIR. These results provide evidence that GIIR can occur in muscle without increased accumulation of hexosamine pathway end products, that neither high glycogen concentration nor impaired insulin signaling is responsible for GIIR, and that synthesis of a protein with a short half-life mediates GIIR. They also suggest that dephosphorylation of a transcription factor may be involved in the induction of GIIR.
Topics: Animals; Enzyme Inhibitors; Glucose; Glucose-6-Phosphate; In Vitro Techniques; Insulin; Insulin Resistance; Male; Muscle Proteins; Muscle, Skeletal; Naphthalenes; Protein Kinase C; Rats; Rats, Wistar; Signal Transduction
PubMed: 11274201
DOI: 10.1074/jbc.M010599200