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.Univ Fed Rio de Janeiro, Inst Bioquim Med, CCS, BR-21541590 Rio de Janeiro, BrazilUniv Fed Rio de Janeiro, Inst Microbiol Prof Paulo Goes, CCS, BR-21541590 Rio de Janeiro, BrazilUNIFESP, Disciplina Biol Celular, São Paulo, BrazilUNIFESP, Disciplina Biol Celular, São Paulo, BrazilWeb of Scienc
