title: Kinetic characterization of P-type membrane ATPase from Streptococcus mutans.
abstract: The proton translocating membrane ATPase of oral streptococci has been implicated in cytoplasmatic pH regulation, acidurance and cariogenicity. Studies have confirmed that Streptococcus mutans is the most frequently detected species in dental caries. A P-type ATPase that can act together with F(1)F(o)-ATPase in S. mutans membrane has been recently described. The main objective of this work is to characterize the kinetic of ATP hydrolysis of this P-type ATPase. The optimum pH for ATP hydrolysis is around 6.0. The dependence of P-type ATPase activity on ATP concentration reveals high (K(0.5)=0.27 mM) and low (K(0.5)=3.31 mM) affinity sites for ATP, exhibiting positive cooperativity and a specific activity of about 74 U/mg. Equimolar concentrations of ATP and magnesium ions display a behavior similar to that described for ATP concentration in Mg(2+) saturating condition (high affinity site, K(0.5)=0.10 mM, and low affinity site, K(0.5)=2.12 mM), exhibiting positive cooperativity and a specific activity of about 68 U/mg. Sodium, potassium, ammonium, calcium and magnesium ions stimulate the enzyme, showing a single saturation curve, all exhibiting positive cooperativities, whereas inhibition of ATPase activity is observed for zinc ions and EDTA. The kinetic characteristics reveal that this ATPase belongs to type IIIA, like the ones found in yeast and plants.
authors.affiliation: Faculdade de Filosofia Ciências e Letras de Ribeirão Preto-FFCLRP-USP, Av. Bandeirantes 3900, Departamento de Química, 14040-901 Ribeirão Preto, SP, Brazil.
authors.forename: Prislaine P
authors.initials: PP
authors.lastname: Magalhães
authors.forename: Tony P
authors.initials: TP
authors.lastname: Paulino
authors.forename: Geraldo
authors.initials: G
authors.lastname: Thedei
authors.forename: Pietro
authors.initials: P
authors.lastname: Ciancaglini
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D025243:Bacterial Proton-Translocating ATPases / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism; D017301:Ca(2+) Mg(2+)-ATPase / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D002384:Catalysis; D004492:Edetic Acid / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008565:Membrane Proteins / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology; D006180:Proton-Translocating ATPases / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology; D013045:Species Specificity; D013295:Streptococcus mutans / Q000187:drug effects / Q000201:enzymology* / Q000254:growth & development; D015032:Zinc / Q000494:pharmacology
chemical_list: D008565:Membrane Proteins; D000644:Quaternary Ammonium Compounds; D000255:Adenosine Triphosphate; D004492:Edetic Acid; D012964:Sodium; D025243:Bacterial Proton-Translocating ATPases; D017301:Ca(2+) Mg(2+)-ATPase; D006180:Proton-Translocating ATPases; D008274:Magnesium; D015032:Zinc; D011188:Potassium; D002118:Calcium