Characterization of an ecto-5′-nucleotidase (EC 3.1.3.5) activity in intact trophozoites of Trichomonas gallinae

This study describes the enzymatic properties of an ecto-5′-nucleotidase in Trichomonas gallinae. The enzyme hydrolyzes nucleoside monophosphates at pH 7.2 and is activated by divalent cations, such as magnesium. Ecto-5′-nucleotidase activity was insensitive to levamisole, tetramisole (alkaline phosphatase inhibitors), and AMPCP (adenosine 5′-[α,β-methylene]diphosphate), an ecto-5′-nucleotidase inhibitor, whereas 0.1 mM ammonium molybdate (considered a potent inhibitor of 5′-nucleotidase activity) completely inhibited the enzyme activity. The apparent KM (Michaelis constant) and Vmax (maximum velocity) values for Mg2+-AMP were 466 ± 57 μM and 3.7 ± 0.59 nmolPi/min/106 trichomonads, respectively. Considering that trichomonads lack the ability to synthesize purines and pyrimidines de novo, the presence of an ecto-5′-nucleotidase in intact trophozoites of T. gallinae could be important in regulating the extracellular nucleotide levels and generating adenosine, essential for the survival strategies of the parasite.