Biochemical characterization of an ecto-ATP diphosphohydrolase activity in Candida parapsilosis and its possible role in adenosine acquisition and pathogenesis
2010
Kiffer-Moreira, Tina | Fernandes Sampaio, Maria Ester | Alviano, Daniela S. | Axelband, Flavia | Cesar, Gabriele Vargas | Cosentino-Gomes, Daniela | Rodrigues, Marcio L. | Nimrichter, Leonardo | Vieyra, Adalberto | Alviano, Celuta S. | Meyer-Fernandes, José Roberto
In this work, we describe the ability of intact cells of Candida parapsilosis to hydrolyze extracellular ATP. ATP hydrolysis was stimulated by MgCl₂ in a dose-dependent manner. The ecto-ATPase activity was increased in the presence of 5 mM MgCl₂, with values of Vmax and apparent Km for Mg-ATP²⁻ increasing to 33.80 ± 1.2 nmol Pi h⁻¹ 10⁻⁸ cells and 0.6 ± 0.06 mM, respectively. Inhibitors of phosphatases, mitochondrial Mg²⁺-ATPases and Na⁺-ATPases had no effect on the C. parapsilosis Mg²⁺-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-β-γ-dibromomethylene ATP), a nucleotide analogue, also inhibited the ecto-ATPase activity in a dose-dependent manner. ATP was the best substrate for the yeast Mg²⁺-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.
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