title: Inhibition and kinetic alterations by excess free ATP and ADP of the ATP diphosphohydrolase activity (EC 3.6.1.5) from rat blood platelets.
abstract: ATP diphosphohydrolase (EC 3.6.1.5) catalyzes the hydrolysis of diphospho- and triphosphonucleosides and is activated by divalent cations. The enzyme described in rat blood platelets hydrolyzes Ca(2+)-ATP and Ca(2+)-ADP with a high affinity for these Ca(2+)-nucleotide complexes as substrates. In the present paper, we demonstrate that free ATP or free ADP induces inhibition and kinetic alterations of the enzyme from rat blood platelets. From these results, we draw conclusions about the binding of free nucleotides to the enzyme and their action as inhibitors with respect to calcium-nucleotide complex.
authors.affiliation: Universidade Federal do Rio Grande do Sul, Departamento de Bioquimica Rua Sarmento Leite, Porto Alegre, Brasil.
authors.forename: S S
authors.initials: SS
authors.lastname: Frassetto
authors.forename: R D
authors.initials: RD
authors.lastname: Dias
authors.forename: J J
authors.initials: JJ
authors.lastname: Sarkis
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D001081:Apyrase / Q000037:antagonists & inhibitors* / Q000097:blood; D001665:Binding Sites; D001792:Blood Platelets / Q000201:enzymology*; D002118:Calcium / Q000378:metabolism; D002413:Cations, Divalent; D004789:Enzyme Activation; D007700:Kinetics; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D013379:Substrate Specificity
chemical_list: D002413:Cations, Divalent; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D001081:Apyrase; D002118:Calcium