title: Inhibition of bovine kidney low molecular mass phosphotyrosine protein phosphatase by uric acid.
abstract: Uric acid inhibited 50% of the activity of bovine kidney low molecular mass phosphotyrosine protein phosphatase at concentrations of 1.0, 0.4, 1.3, and 0.2 mM, respectively for p-nitrophenyl phosphate (p-NPP), flavine mononucleotide, beta-naphthyl phosphate and tyrosine phosphate (Tyr-P) as substrates. The mixed type inhibition of p-NPP hydrolysis was fully reversible, with Kic and Kiu values of 0.4 and 1.1 mM, respectively; the inhibition by uric acid shifted the pH optimum from 5.0 to 6.5. When Tyr-P was the substrate, competitive inhibition was observed with a Ki value of 0.05 mM. Inhibition studies by uric acid in the presence of thiol compounds, and preincubation studies in the presence of inorganic phosphate suggest that the interaction of uric acid with the enzyme occurred at the active site, but did not involve SH residues, and that the mechanism of inhibition depended on the structure of the substrates.
authors.affiliation: Departamento de Físico-Química, IQ, UNICAMP, Cidade Universitária, CEP 13083-970 CAMPINAS, São Paulo, Brasil.
authors.forename: José Mauro
authors.initials: JM
authors.lastname: Granjeiro
authors.forename: Carmen Verissima
authors.initials: CV
authors.lastname: Ferreira
authors.forename: Paulo Afonso
authors.initials: PA
authors.lastname: Granjeiro
authors.forename: Cinthia Celestino
authors.initials: CC
authors.lastname: Da Silva
authors.forename: Eulázio Mikio
authors.initials: EM
authors.lastname: Taga
authors.forename: Pedro Luiz Onofre
authors.initials: PL
authors.lastname: Volpe
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Aoyama
mesh_terms: D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D002417:Cattle; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005486:Flavin Mononucleotide / Q000378:metabolism; D007668:Kidney / Q000187:drug effects / Q000201:enzymology*; D007700:Kinetics; D009281:Naphthalenes / Q000378:metabolism; D009596:Nitrophenols / Q000378:metabolism; D010755:Organophosphates / Q000378:metabolism; D009943:Organophosphorus Compounds / Q000378:metabolism; D010710:Phosphates / Q000494:pharmacology; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors*; D013379:Substrate Specificity; D013438:Sulfhydryl Compounds / Q000494:pharmacology; D014443:Tyrosine / Q000378:metabolism; D014527:Uric Acid / Q000494:pharmacology*
chemical_list: D004791:Enzyme Inhibitors; D009281:Naphthalenes; D009596:Nitrophenols; D010755:Organophosphates; D009943:Organophosphorus Compounds; D010710:Phosphates; D013438:Sulfhydryl Compounds; C107072:beta-naphthyl phosphate; D014527:Uric Acid; C008644:nitrophenylphosphate; D014443:Tyrosine; D005486:Flavin Mononucleotide; D017027:Protein Tyrosine Phosphatases