title: Divalent cation dependence and inhibition of Schistosoma mansoni ATP diphosphohydrolase by fluorosulfonylbenzoyl adenosine.
abstract: Hydrolysis of ATP or ADP catalyzed by the ATP diphosphohydrolase of Schistosoma mansoni tegument was measured in the presence of different cations. ATP diphosphohydrolase was stimulated by micromolar concentrations of either Ca2+ or Mg2+, Ca2+ producing threefold higher maximal activities than Mg2+. Kinetic studies indicated that Ca2+ and Mg2+ compete for the same binding site on the enzyme. The effect of covalent labeling of ATP diphosphohydrolase with the ATP analog fluorosulfonylbenzoyl adenosine (FSO2BzAdo) was studied. Schistosome tegument was passed through with Sephadex G-50 filtration centrifugation columns to remove endogenous nucleotides, and this was followed by labeling with FSO2BzAdo. Incubation of ATP diphosphohydrolase with 1 mM FSO2BzAdo for 1 h inhibited ATPase or ADPase activities by 60% and 50%, respectively. Addition of ATP together with FSO2BzAdo provided greater than 90% protection against FSO2BzAdo inactivation, indicating that FSO2BzAdo binds to an ATP-binding site on the ATP diphosphohydrolase. Furthermore, addition of FSO2BzAdo to a medium containing intact worms caused 30% and 50% inhibition of ATPase and ADPase activities, respectively, indicating that the ATP-binding site of diphosphohydrolase is accessible to FSO2BzAdo from the external surface of S. mansoni worms.
authors.affiliation: Departamento de Bioquímica Médica, Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Brazil.
authors.forename: C R
authors.initials: CR
authors.lastname: Torres
authors.forename: E G
authors.initials: EG
authors.lastname: Vasconcelos
authors.forename: S T
authors.initials: ST
authors.lastname: Ferreira
authors.forename: S
authors.initials: S
authors.lastname: Verjovski-Almeida
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology; D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001081:Apyrase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D002412:Cations / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006868:Hydrolysis; D008274:Magnesium / Q000494:pharmacology; D008958:Models, Molecular; D012550:Schistosoma mansoni / Q000187:drug effects / Q000201:enzymology*
chemical_list: D002412:Cations; D004791:Enzyme Inhibitors; D000244:Adenosine Diphosphate; C010959:5'-(4-fluorosulfonylbenzoyl)adenosine; D000255:Adenosine Triphosphate; D001081:Apyrase; D008274:Magnesium; D000241:Adenosine