Hydrogenosomal ATP:AMP phosphotransferase of Trichomonas vaginalis

1. ATP:AMP phosphotransferase (adenylate kinase) is present in Trichomonas vaginalis, primarily with hydrogenosomal localization. 2. Adenylate kinase has been purified from hydrogenosome-enriched fractions by solubilization with Triton X-100 and KCl followed by affinity chromatography and gel filtration. 3. The enzyme has a Mr = 28,000, a broad pH optimum of pH 7-9, requirement for Mg2+ and specificity for adenine and deoxyadenine nucleotides. 4. The activity is competetively inhibited by P1,P5-di(adenosine-5') pentaphosphate (Ki 200 nM) and reversibly inactivated by 5,5'-dithiobis-(2-nitrobenzoate). 5. Catalytic properties of this enzyme are similar to those of enzymes from other organisms. Other properties indicate its uniqueness, however, since its molecular mass and Ki for P1,P5-di(adenosine-5'-)-pentaphosphate bring it closer to the mitochrondrial isoenzyme, while it shares a requirement for reduced thiol groups with the cytosolic isoenzyme.