Tritrichomonas foetus: purification and characterization of hydrogenosomal ATP:AMP phosphotransferase (adenylate kinase).
The hydrogenosomal enzyme ATP:AMP phosphotransferase (adenylate kinase) (EC 2.7.4.3) was purified to apparent homogeneity from the bovine parasite Tritrichomonas foetus. A fraction enriched for hydrogenosomes was obtained from cell homogenates which had been subjected to differential and isopycnic centrifugation. Adenylate kinase was solubilized in 50 mM Tris-HCl, pH 7.3, containing 0.8% Triton X-100, and purified by sequential Affi-Gel blue affinity chromatography and high-performance liquid chromatography gel filtration. The purified enzyme, a monomer of Mr 29,000, exhibited Km values of 100, 195, and 83 microM for ADP, ATP, and AMP, respectively. Substituting other mono-, di-, and trinucleotides for AMP, ADP, and ATP gave less than half the maximal activity. Full enzyme activity requires Mg2+, but Mn2+ and Co2+ yield half maximal activity. The enzyme has a broad optimal pH range between pH 6 and 9. The enzyme was competitively inhibited by P1,P5-di(adenosine-5')pentaphosphate, a specific adenylate kinase inhibitor: the Ki was 150 nM. The enzyme was also inhibited with 5,5'-dithiobis(2-nitrobenzoic acid), and this inhibition could be reversed by the addition of 2 mM dithiothreitol. T. foetus adenylate kinase has similar catalytic and physical properties to that of the biologically closely related human parasite Trichomonas vaginalis.
Dinbergs
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Department of Biology, Cleveland State University, Ohio 44115.
Lindmark
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D000263:Adenylate Kinase / Q000037:antagonists & inhibitors / Q000302:isolation & purification*; D000818:Animals; D005260:Female; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008970:Molecular Weight; D010770:Phosphotransferases / Q000302:isolation & purification*; D011817:Rabbits; D014244:Trichomonas / Q000201:enzymology*
D010770:Phosphotransferases; D000263:Adenylate Kinase; D008274:Magnesium