Mycelial forms of Pseudallescheria boydii present ectophosphatase activities
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ORIGINAL PAPER
Mycelial forms of Pseudallescheria boydii present ectophosphatase activities Tina KiVer-Moreira · Ana Acacia S. Pinheiro · Márcia R. Pinto · Fabiano F. Esteves · Thais Souto-Padrón · Eliana Barreto-Bergter · José R. Meyer-Fernandes
Received: 28 February 2007 / Revised: 28 February 2007 / Accepted: 5 March 2007 / Published online: 12 April 2007 © Springer-Verlag 2007
Abstract Phosphatase activities were characterized in intact mycelial forms of Pseudallescheria boydii, which are able to hydrolyze the artiWcial substrate p-nitrophenylphosphate (p-NPP) to p-nitrophenol (p-NP) at a rate of 41.41 § 2.33 nmol p-NP per h per mg dry weight, linearly with increasing time and with increasing cell density. MgCl2, MnCl2 and ZnCl2 were able to increase the (pNPP) hydrolysis while CdCl2 and CuCl2 inhibited it. The (p-NPP) hydrolysis was enhanced by increasing pH values (2.5-8.5) over an approximately 5-fold range. High sensitivity to speciWc inhibitors of alkaline and acid phosphatases suggests the presence of both acid and alkaline phosphatase activities on P. boydii mycelia surface. Cytochemical localization of the acid and alkaline phosphatase showed electron-dense cerium phosphate deposits on the cell wall, as visualized by electron microscopy. The product of p-NPP hydrolysis, inorganic phosphate (Pi), and diVerent inhibitors for phosphatase activities inhibited pNPP hydrolysis in a dose-dependent manner, but only the inhibition promoted by sodium orthovanadate and ammonium molybdate is irreversible. Intact mycelial forms of P. boydii are also able to hydrolyze phosphoaminoacids with diVerent speciWcity.
T. KiVer-Moreira · A. A. S. Pinheiro · F. F. Esteves · J. R. Meyer-Fernandes (&) Instututo de Bioquímica Médica, Universidade Federal do Rio de Janeiro, CCS, bloco H, Cidade Universitária, Rio de Janeiro, RJ, 21941-590, Brazil e-mail: [email protected] M. R. Pinto · T. Souto-Padrón · E. Barreto-Bergter Instituto de Microbiologia Prof. Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, 21941-590, Brazil
Keywords Pseudallescheria boydii · Phosphatase activities · Ecto-enzymes
Introduction Pseudallescheria boydii belongs to the class Ascomycetes and is the perfect (sexual) form of Scedosporium apiospermum. It is a natural saphrophyte that is commonly found in soil and polluted water (Rippon 1998). The most common clinical condition in immunocompetent patients involving P. boydii is mycetoma (chronic infection of the skin and subcutaneous tissues) (Bakerspiegel 1971; Baxter et al. 1996). Immunocompromised patients are at higher risk for locally invasive or disseminated Pseudallescheria infection due to increased incidence of human immunodeWciency virus infection, antineoplasic or immunosuppressive therapy (Berenguer et al. 1989; Patterson et al. 1990). Several kinds of therapies against P. boydii infection have been used but the treatment is problematic, since this fungus frequently exhibits resistance to amphotericin B (Nielsen 1967; Ginter et al. 1999). In this context, the charac
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