title: Hydrolysis of tripolyphosphate by purified exopolyphosphatase from Saccharomyces cerevisiae cytosol: kinetic model.
abstract: The kinetics of hydrolysis of tripolyphosphate by purified exopolyphosphatase from Saccharomyces cerevisiae cytosol has been studied in the presence of Mg2+. Two kinetic models suggesting the formation of complexes of tripolyphosphate and the enzyme with Mg2+ are compared. Both models suggest that only enzyme--substrate complexes containing Mg2+ and tripolyphosphate simultaneously are able to hydrolyze the tripolyphosphate. The first model suggests that the enzyme is able to bind to Mg2+ independently from substrate binding. The second model does not consider this possibility, but suggests that both complexes containing tripolyphosphate and Mg2+ in proportion 1:1 and 1:2 can serve as the reaction substrates. The description of the experimental data by both models is essentially the same. The complex containing tripolyphosphate and Mg2+ in proportion 1:1 is optimal for the enzyme activity, the complex containing tripolyphosphate and Mg2+ in proportion 1:2 being hydrolyzed at a lower rate.
authors.affiliation: Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, Pushchino, Moscow Region, 142292, Russia. alla@ibpm.serpukhov.su
authors.forename: T V
authors.initials: TV
authors.lastname: Kulakovskaya
authors.forename: N A
authors.initials: NA
authors.lastname: Andreeva
authors.forename: A V
authors.initials: AV
authors.lastname: Karpov
authors.forename: I A
authors.initials: IA
authors.lastname: Sidorov
authors.forename: I S
authors.initials: IS
authors.lastname: Kulaev
mesh_terms: D017766:Acid Anhydride Hydrolases / Q000302:isolation & purification / Q000378:metabolism*; D003600:Cytosol / Q000201:enzymology; D006868:Hydrolysis; D007700:Kinetics; D008274:Magnesium / Q000378:metabolism; D008962:Models, Theoretical; D011122:Polyphosphates / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology*
chemical_list: D011122:Polyphosphates; D017766:Acid Anhydride Hydrolases; C020137:exopolyphosphatase; D008274:Magnesium; C005692:triphosphoric acid