Publications

• The effect of carbonic anhydrase inhibition on the velocity of thrombin-stimulated platelet aggregation under physiological conditions.

  Siffert W., Fox G., Gros G.

  We have studied the effect of ethoxzolamide , a specific carbonic anhydrase inhibitor, on the velocity of thrombin-stimulated platelet aggregation. After preincubation of platelet rich plasma with 10(-6) M ethoxzolamide the velocity of platelet aggregation was reduced by about 40%. Between 10(-11) ... >> More

  We have studied the effect of ethoxzolamide , a specific carbonic anhydrase inhibitor, on the velocity of thrombin-stimulated platelet aggregation. After preincubation of platelet rich plasma with 10(-6) M ethoxzolamide the velocity of platelet aggregation was reduced by about 40%. Between 10(-11) M and 10(-10)M ethoxzolamide was necessary to achieve a half-maximal diminution of the aggregation velocity. An identical maximal reduction of the velocity of aggregation as with ethoxzolamide could be achieved by a nearly complete removal of CO2 from the platelet rich plasma. These results suggest that the intracellular CO2 hydration-dehydration reaction is involved in the activation of human platelets by thrombin. It is possible that the cytosolic carbonic anhydrase of platelets provides a rapid source of the protons that are transferred across the plasma membrane during the activation process. << Less

  Biochem Biophys Res Commun 121:266-270(1984) [PubMed] [EuropePMC]

  This publication is cited by 3 other entries.

• Crystal structure of a UDP-glucose-specific glycosyltransferase from a Mycobacterium species.

  Fulton Z., McAlister A., Wilce M.C., Brammananth R., Zaker-Tabrizi L., Perugini M.A., Bottomley S.P., Coppel R.L., Crellin P.K., Rossjohn J., Beddoe T.

  Glycosyltransferases (GTs) are a large and ubiquitous family of enzymes that specifically transfer sugar moieties to a range of substrates. Mycobacterium tuberculosis contains a large number of GTs, many of which are implicated in cell wall synthesis, yet the majority of these GTs remain poorly ch ... >> More

  Glycosyltransferases (GTs) are a large and ubiquitous family of enzymes that specifically transfer sugar moieties to a range of substrates. Mycobacterium tuberculosis contains a large number of GTs, many of which are implicated in cell wall synthesis, yet the majority of these GTs remain poorly characterized. Here, we report the high resolution crystal structures of an essential GT (MAP2569c) from Mycobacterium avium subsp. paratuberculosis (a close homologue of Rv1208 from M. tuberculosis) in its apo- and ligand-bound forms. The structure adopted the GT-A fold and possessed the characteristic DXD motif that coordinated an Mn(2+) ion. Atypical of most GTs characterized to date, MAP2569c exhibited specificity toward the donor substrate, UDP-glucose. The structure of this ligated complex revealed an induced fit binding mechanism and provided a basis for this unique specificity. Collectively, the structural features suggested that MAP2569c may adopt a "retaining" enzymatic mechanism, which has implications for the classification of other GTs in this large superfamily. << Less

  J. Biol. Chem. 283:27881-27890(2008) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• Characterization of the biosynthetic pathway of glucosylglycerate in the archaeon Methanococcoides burtonii.

  Costa J., Empadinhas N., Goncalves L., Lamosa P., Santos H., da Costa M.S.

  The pathway for the synthesis of the organic solute glucosylglycerate (GG) is proposed based on the activities of the recombinant glucosyl-3-phosphoglycerate synthase (GpgS) and glucosyl-3-phosphoglycerate phosphatase (GpgP) from Methanococcoides burtonii. A mannosyl-3-phosphoglycerate phosphatase ... >> More

  The pathway for the synthesis of the organic solute glucosylglycerate (GG) is proposed based on the activities of the recombinant glucosyl-3-phosphoglycerate synthase (GpgS) and glucosyl-3-phosphoglycerate phosphatase (GpgP) from Methanococcoides burtonii. A mannosyl-3-phosphoglycerate phosphatase gene homologue (mpgP) was found in the genome of M. burtonii (http://www.jgi.doe.gov), but an mpgS gene coding for mannosyl-3-phosphoglycerate synthase (MpgS) was absent. The gene upstream of the mpgP homologue encoded a putative glucosyltransferase that was expressed in Escherichia coli. The recombinant product had GpgS activity, catalyzing the synthesis of glucosyl-3-phosphoglycerate (GPG) from GDP-glucose and d-3-phosphoglycerate, with a high substrate specificity. The recombinant MpgP protein dephosphorylated GPG to GG and was also able to dephosphorylate mannosyl-3-phosphoglycerate (MPG) but no other substrate tested. Similar flexibilities in substrate specificity were confirmed in vitro for the MpgPs from Thermus thermophilus, Pyrococcus horikoshii, and "Dehalococcoides ethenogenes." GpgS had maximal activity at 50 degrees C. The maximal activity of GpgP was at 50 degrees C with GPG as the substrate and at 60 degrees C with MPG. Despite the similarity of the sugar donors GDP-glucose and GDP-mannose, the enzymes for the synthesis of GPG or MPG share no amino acid sequence identity, save for short motifs. However, the hydrolysis of GPG and MPG is carried out by phosphatases encoded by homologous genes and capable of using both substrates. To our knowledge, this is the first report of the elucidation of a biosynthetic pathway for glucosylglycerate. << Less

  J. Bacteriol. 188:1022-1030(2006) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• Glucosylglycerate biosynthesis in the deepest lineage of the Bacteria: characterization of the thermophilic proteins GpgS and GpgP from Persephonella marina.

  Costa J., Empadinhas N., da Costa M.S.

  The pathway for the synthesis of glucosylglycerate (GG) in the thermophilic bacterium Persephonella marina is proposed based on the activities of recombinant glucosyl-3-phosphoglycerate (GPG) synthase (GpgS) and glucosyl-3-phosphoglycerate phosphatase (GpgP). The sequences of gpgS and gpgP from th ... >> More

  The pathway for the synthesis of glucosylglycerate (GG) in the thermophilic bacterium Persephonella marina is proposed based on the activities of recombinant glucosyl-3-phosphoglycerate (GPG) synthase (GpgS) and glucosyl-3-phosphoglycerate phosphatase (GpgP). The sequences of gpgS and gpgP from the cold-adapted bacterium Methanococcoides burtonii were used to identify the homologues in the genome of P. marina, which were separately cloned and overexpressed as His-tagged proteins in Escherichia coli. The recombinant GpgS protein of P. marina, unlike the homologue from M. burtonii, which was specific for GDP-glucose, catalyzed the synthesis of GPG from UDP-glucose, GDP-glucose, ADP-glucose, and TDP-glucose (in order of decreasing efficiency) and from d-3-phosphoglycerate, with maximal activity at 90 degrees C. The recombinant GpgP protein, like the M. burtonii homologue, dephosphorylated GPG and mannosyl-3-phosphoglycerate (MPG) to GG and mannosylglycerate, respectively, yet at high temperatures the hydrolysis of GPG was more efficient than that of MPG. Gel filtration indicates that GpgS is a dimeric protein, while GpgP is monomeric. This is the first characterization of genes and enzymes for the synthesis of GG in a thermophile. << Less

  J. Bacteriol. 189:1648-1654(2007) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• Identification of the mycobacterial glucosyl-3-phosphoglycerate synthase.

  Empadinhas N., Albuquerque L., Mendes V., Macedo-Ribeiro S., da Costa M.S.

  Mycobacteria synthesize unique polysaccharides that regulate fatty acid synthesis, namely the methylglucose lipopolysaccharide (MGLP) and the methylmannose polysaccharide. Glucosyl-(1-->2)-glycerate is found at the reducing end of MGLP. The mycobacterial gene encoding a glucosyl-3-phosphoglycerate ... >> More

  Mycobacteria synthesize unique polysaccharides that regulate fatty acid synthesis, namely the methylglucose lipopolysaccharide (MGLP) and the methylmannose polysaccharide. Glucosyl-(1-->2)-glycerate is found at the reducing end of MGLP. The mycobacterial gene encoding a glucosyl-3-phosphoglycerate synthase (GpgS), primarily found in actinobacteria and sharing very low amino acid identity with known homo-functional GpgSs, has been identified. This gene has been annotated as an inverting family 2 glycosyltransferase of unknown function. The gpgS genes from the fast-growing Mycobacterium smegmatis strain 1102 and from the slow-growing Mycobacterium bovis BCG in Escherichia coli were expressed, and the recombinant enzymes were purified and characterized. The substrates for optimal activity were UDP-glucose and d-3-phosphoglycerate but ADP-glucose was also an efficient donor. The enzymes had maximal activity around 45 degrees C, pH 8.0, and were strictly dependent on Mg(2+). In Mycobacterium tuberculosis H37Rv, the gene encoding GpgS (Rv1208) is identical to the homologue in Mycobacterium bovis BCG and was considered to be essential for growth. It is shown that these genes encode retaining family 81 glycosyltransferases regardless of the low amino acid identity with other known enzymes of this family. << Less

  FEMS Microbiol. Lett. 280:195-202(2008) [PubMed] [EuropePMC]

  This publication is cited by 3 other entries.

• Two alternative pathways for the synthesis of the rare compatible solute mannosylglucosylglycerate in Petrotoga mobilis.

  Fernandes C., Mendes V., Costa J., Empadinhas N., Jorge C., Lamosa P., Santos H., da Costa M.S.

  The compatible solute mannosylglucosylglycerate (MGG), recently identified in Petrotoga miotherma, also accumulates in Petrotoga mobilis in response to hyperosmotic conditions and supraoptimal growth temperatures. Two functionally connected genes encoding a glucosyl-3-phosphoglycerate synthase (Gp ... >> More

  The compatible solute mannosylglucosylglycerate (MGG), recently identified in Petrotoga miotherma, also accumulates in Petrotoga mobilis in response to hyperosmotic conditions and supraoptimal growth temperatures. Two functionally connected genes encoding a glucosyl-3-phosphoglycerate synthase (GpgS) and an unknown glycosyltransferase (gene Pmob_1143), which we functionally characterized as a mannosylglucosyl-3-phosphoglycerate synthase and designated MggA, were identified in the genome of Ptg. mobilis. This enzyme used the product of GpgS, glucosyl-3-phosphoglycerate (GPG), as well as GDP-mannose to produce mannosylglucosyl-3-phosphoglycerate (MGPG), the phosphorylated precursor of MGG. The MGPG dephosphorylation was determined in cell extracts, and the native enzyme was partially purified and characterized. Surprisingly, a gene encoding a putative glucosylglycerate synthase (Ggs) was also identified in the genome of Ptg. mobilis, and an active Ggs capable of producing glucosylglycerate (GG) from ADP-glucose and d-glycerate was detected in cell extracts and the recombinant enzyme was characterized, as well. Since GG has never been identified in this organism nor was it a substrate for the MggA, we anticipated the existence of a nonphosphorylating pathway for MGG synthesis. We putatively identified the corresponding gene, whose product had some sequence homology with MggA, but it was not possible to recombinantly express a functional enzyme from Ptg. mobilis, which we named mannosylglucosylglycerate synthase (MggS). In turn, a homologous gene from Thermotoga maritima was successfully expressed, and the synthesis of MGG was confirmed from GDP-mannose and GG. Based on the measurements of the relevant enzyme activities in cell extracts and on the functional characterization of the key enzymes, we propose two alternative pathways for the synthesis of the rare compatible solute MGG in Ptg. mobilis. << Less

  J. Bacteriol. 192:1624-1633(2010) [PubMed] [EuropePMC]

  This publication is cited by 4 other entries.