Open AccessCharacterization of an ecto‐ATPase activity in Cryptococcus neoformans
Author(s) -
Junior Itallo Collopy,
Rodrigues Marcio L.,
Alviano Celuta S.,
Travassos Luiz R.,
MeyerFernandes José Roberto
Publication year - 2005
Publication title -
fems yeast research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.991
H-Index - 92
eISSN - 1567-1364
pISSN - 1567-1356
DOI - 10.1016/j.femsyr.2005.04.005
Subject(s) - cryptococcus neoformans , biology , atpase , adenosine triphosphate , atp hydrolysis , biochemistry , enzyme , extracellular , inosine , guanosine triphosphate , gtp' , microbiology and biotechnology
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 × 10 8 cells. In the presence of 5 mM MgCl 2 , 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 Mg 2+ ‐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 ecto‐ATPase that may have a role in fungal physiology.