title: ADP-ribosyltransferase in Plasmodium (malaria parasites).
abstract: The nuclei of Plasmodium yoelii nigeriensis contain an enzyme, ADP-ribosyltransferase, that will incorporate the ADP-ribose moiety of NAD+ into acid-insoluble product. The time, pH and temperature optima of this incorporation are 30 min, 8.5 and 25 degrees C respectively. Maximum stimulation of the enzyme activity is obtained with 1.0 mM-dithiothreitol or 2.0 mM-2-mercaptoethanol. Ca2+ and Mg2+ ions at optimum concentrations of 5 mM and 10 mM respectively stimulated the activity of the enzyme by 21% and 91%. The enzyme activity is, however, inhibited by 24% in the presence of 10 mM-MnSO4. The substrate, NAD+, exhibits an apparent Km of 500 microM, and the activity of the enzyme is inhibited by four chemical classes of inhibitors: nicotinamides, methylxanthines, thymidine and aromatic amides. The inhibitors are effective in the following increasing order: nicotinamide less than 3-aminobenzamide less than thymidine less than 5-methylnicotinamide less than theophylline less than m-methoxybenzamide less than theobromine. The enzyme activity is also inhibited by some DNA-binding anti-malarial drugs.
mesh_terms: D000818:Animals; D000962:Antimalarials / Q000494:pharmacology; D002413:Cations, Divalent / Q000494:pharmacology; D002467:Cell Nucleus / Q000201:enzymology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008291:Malate Dehydrogenase / Q000378:metabolism; D009713:Nucleotidyltransferases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010961:Plasmodium / Q000201:enzymology*; D011064:Poly Adenosine Diphosphate Ribose / Q000378:metabolism; D011065:Poly(ADP-ribose) Polymerases; D013439:Sulfhydryl Reagents / Q000494:pharmacology; D013696:Temperature
chemical_list: D000962:Antimalarials; D002413:Cations, Divalent; D013439:Sulfhydryl Reagents; D011064:Poly Adenosine Diphosphate Ribose; D008291:Malate Dehydrogenase; D011065:Poly(ADP-ribose) Polymerases; D009713:Nucleotidyltransferases