Inorganic pyrophosphatase of Trichomonas vaginalis

Trichomonas vaginalis homogenates were found to have an acid inorganic pyrophosphatase activity with a specific activity at pH 4.8 of about 7 nmol min-1 (mg protein)-1. This activity was localized predominantly in hydrolase containing particles, showed structure-bound latency and was tightly membrane-bound. The activity showed no magnesium dependence, a Km of about 2 mM inorganic pyrophosphate, a pH optimum of 5.2 and was inhibited by fluoride at millimolar levels. No evidence was obtained for the existence of a cytosolic magnesium-dependent activity but the existence of a low level of magnesium-independent cytosolic activity cannot be excluded. These observations correlate with the importance of cytosolic inorganic pyrophosphate in the carbohydrate catabolism in T. vaginalis.