Guanosine kinase from Trichomonas vaginalis.
A novel guanosine kinase was partially purified from the parasitic protozoan Trichomonas vaginalis. Unlike nucleoside kinases from other sources, the preferred substrate for this enzyme was guanosine (Vmax/Km = 120). The enzyme also catalyzed the phosphorylation of inosine (Vmax/Km = 3), uridine (2), adenosine (0.5), cytidine (0.2), and 2'-deoxyguanosine (0.1). The 2'-deoxyribonucleosides of adenine, hypoxanthine, uracil, cytosine and thymine were not phosphorylated. The Km for ATP was 6.6 microM. The enzyme was extremely labile in the absence of ATP. As a result, only a 20-fold purification with 25% recovery of activity was possible. However, this preparation was free of nucleoside phosphorylase, nucleoside phosphotransferase and the distinct uridine kinase. The enzyme had a broad optimum of pH 6.5-8. It had a molecular weight of 15000.
Miller
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Division of Experimental Therapy, Wellcome Research Laboratories, Research Triangle Park, NC 27709.
Miller
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D000818:Animals; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009705:Nucleosides; D010710:Phosphates; D010770:Phosphotransferases / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor); D011489:Protein Denaturation; D013379:Substrate Specificity; D014246:Trichomonas vaginalis / Q000201:enzymology*
D009705:Nucleosides; D010710:Phosphates; D010770:Phosphotransferases; D017853:Phosphotransferases (Alcohol Group Acceptor); C055032:guanosine kinase