title: Polyphosphates strongly inhibit the tRNA dependent synthesis of poly(A) catalyzed by poly(A) polymerase from Saccharomyces cerevisiae.
abstract: Polyphosphates of different chain lengths (P(3), P(4), P(15), P(35)), (1 microM) inhibited 10, 60, 90 and 100%, respectively, the primer (tRNA) dependent synthesis of poly(A) catalyzed poly(A) polymerase from Saccharomyces cerevisiae. The relative inhibition evoked by p(4)A and P(4) (1 microM) was 40 and 60%, respectively, whereas 1 microM Ap(4)A was not inhibitory. P(4) and P(15) were assayed as inhibitors of the enzyme in the presence of (a) saturating tRNA and variable concentrations of ATP and (b) saturating ATP and variable concentrations of tRNA. In (a), P(4) and P(15) behaved as competitive inhibitors, with K(i) values of 0.5 microM and 0.2 microM, respectively. In addition, P(4) (at 1 microM) and P(15) (at 0.3 microM) changed the Hill coefficient (n(H)) from 1 (control) to about 1.3 and 1.6, respectively. In (b), the inhibition by P(4) and P(15) decreased V and modified only slightly the K(m) values of the enzyme towards tRNA.
authors.affiliation: Departamento de Bioquímica, Instituto de Investigaciones Biomédicas Alberto Sols UAM/CSIC, Facultad de Medicina, 28029 Madrid, Spain.
authors.forename: María A Günther
authors.initials: MA
authors.lastname: Sillero
authors.forename: Anabel
authors.initials: A
authors.lastname: de Diego
authors.forename: Eduardo
authors.initials: E
authors.lastname: Silles
authors.forename: Hugo
authors.initials: H
authors.lastname: Osorio
authors.forename: Antonio
authors.initials: A
authors.lastname: Sillero
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D002384:Catalysis; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007700:Kinetics; D011061:Poly A / Q000096:biosynthesis*; D011062:Polynucleotide Adenylyltransferase / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D011122:Polyphosphates / Q000494:pharmacology*; D012343:RNA, Transfer / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D004791:Enzyme Inhibitors; D011122:Polyphosphates; D029701:Saccharomyces cerevisiae Proteins; D011061:Poly A; D000255:Adenosine Triphosphate; D012343:RNA, Transfer; D011062:Polynucleotide Adenylyltransferase