Characterization of an ecto-ATPase activity in Cryptococcus neoformans

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Junior, I. C.
Rodrigues, M. L.
Alviano, C. S.
Travassos, Luiz Rodolpho [UNIFESP]
Meyer-Fernandes, JR
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Cryptococcus neoformans is the causative agent of pulmonary cryptococcosis and cryptococcal meningoencephalitis, which are major clinical manifestations in immunosuppressed patients. in the present study, a surface ATPase (ecto-ATPase) was identified in C. neoformans yeast cells. Intact yeasts hydrolyzed adenosine-5'-triphosphate (ATP) at a rate of 29.36 +/- 3.36 nmol Pi/h x 10(8) cells. in the presence of 5 mM MgCl2, this activity was enhanced around 70 times, and an apparent K-m for Mg-ATP corresponding to 0.61 mM was determined. Inhibitors of phosphatases, mitochondrial Mg2+-ATPases, V-ATPases, Na+-ATPases or P-ATPases had no effect on the cryptococcal ATPase, but extracellular impermeant compounds reduced enzyme activity in living cells. ATP was the best substrate for the cryptococcal ecto-enzyme, but it also efficiently hydrolyzed inosine 5'-triphosphate (ITP), cytidine 5'-triphosphate (CTP), guanosine 5'-triphosphate (GTP) and uridine-5'-triphosphate (UTP). in the presence of ATP, C. neoformans became less susceptible to the antifungal action of fluconazole. Our results are indicative of the occurrence of a C. neoformans ectoATPase that may have a role in fungal physiology. (c) 2005 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved.
Fems Yeast Research. Amsterdam: Elsevier B.V., v. 5, n. 10, p. 899-907, 2005.