title: Biochemical characterization of an ecto-ATP diphosphohydrolase activity in Candida parapsilosis and its possible role in adenosine acquisition and pathogenesis.
abstract: In this work, we describe the ability of intact cells of Candida parapsilosis to hydrolyze extracellular ATP. ATP hydrolysis was stimulated by MgCl(2) in a dose-dependent manner. The ecto-ATPase activity was increased in the presence of 5 mM MgCl(2), with values of V(max) and apparent K(m) for Mg-ATP(2-) increasing to 33.80 +/- 1.2 nmol Pi h(-1) 10(-8) cells and 0.6 +/- 0.06 mM, respectively. Inhibitors of phosphatases, mitochondrial Mg(2+)-ATPases and Na(+)-ATPases had no effect on the C. parapsilosis Mg(2+)-stimulated ATPase activity, but extracellular impermeant compounds, 4,4'-diisothiocyanatostilbene-2,2'disulfonic acid and suramin, reduced enzyme activity in yeast living cells by 83.1% and 81.9%, respectively. ARL 67156 (6-N,N'-diethyl-d-beta-gamma-dibromomethylene ATP), a nucleotide analogue, also inhibited the ecto-ATPase activity in a dose-dependent manner. ATP was the best substrate for the yeast Mg(2+)-stimulated ecto-enzyme, but ADP, ITP, CTP, GTP and UTP were also hydrolyzed. A direct relationship between ecto-ATPase activity and adhesion to host cells was observed. In these assays, inhibition of enzyme activity resulted in decreased levels of yeast adhesion to epithelial cells. Based also on the differential expression of ecto-ATPase activities in the different isolates of C. parapsilosis, the possible role of this enzyme in fungal biology is discussed.
authors.affiliation: Instituto de Bioquímica Médica, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil. meyer@bioqmed.ufrj.br
authors.forename: Tina
authors.initials: T
authors.lastname: Kiffer-Moreira
authors.forename: Maria Ester
authors.initials: ME
authors.lastname: Fernandes Sampaio
authors.forename: Daniela S
authors.initials: DS
authors.lastname: Alviano
authors.forename: Flavia
authors.initials: F
authors.lastname: Axelband
authors.forename: Gabriele Vargas
authors.initials: GV
authors.lastname: Cesar
authors.forename: Daniela
authors.initials: D
authors.lastname: Cosentino-Gomes
authors.forename: Marcio L
authors.initials: ML
authors.lastname: Rodrigues
authors.forename: Leonardo
authors.initials: L
authors.lastname: Nimrichter
authors.forename: Adalberto
authors.initials: A
authors.lastname: Vieyra
authors.forename: Celuta S
authors.initials: CS
authors.lastname: Alviano
authors.forename: José Roberto
authors.initials: JR
authors.lastname: Meyer-Fernandes
mesh_terms: D000241:Adenosine / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D015703:Antigens, CD / Q000737:chemistry / Q000378:metabolism*; D001081:Apyrase / Q000737:chemistry / Q000378:metabolism*; D002175:Candida / Q000201:enzymology* / Q000472:pathogenicity*; D002448:Cell Adhesion; D003067:Coenzymes / Q000378:metabolism; D006224:Cricetinae; D003412:Cricetulus; D004791:Enzyme Inhibitors / Q000378:metabolism; D004847:Epithelial Cells; D006801:Humans; D007700:Kinetics; D015636:Magnesium Chloride / Q000378:metabolism; D013379:Substrate Specificity; D014774:Virulence; D037521:Virulence Factors / Q000378:metabolism*
chemical_list: D015703:Antigens, CD; D003067:Coenzymes; D004791:Enzyme Inhibitors; D037521:Virulence Factors; D015636:Magnesium Chloride; D000255:Adenosine Triphosphate; D001081:Apyrase; C067869:CD39 antigen; D000241:Adenosine