[Cooperative mechanism of phosphorylation of the monomeric and dimeric forms of inorganic pyrophosphatase from baker's yeast].
A comparative study of phosphorylation of native dimeric and artificial monomeric forms of inorganic pyrophosphatase and its fluoride-stabilized complex with PPi has been carried out. The maximal incorporation of Pi for the dimeric and monomeric proteins is 0.5 and 1 mole per mole of subunit, respectively. The saturation kinetic curves are suggestive of strong positive cooperative interactions. The value of the Hill coefficient (5.5) for the free dimeric enzyme drastically changes upon the active center blockage and/or transition to the monomeric enzyme. Acceleration of dephosphorylation induced by Pi in the presence of Mg2+ is observed only in the case of the dimeric protein. The data obtained indicate that phosphorylation of native dimeric pyrophosphatase occurs according to a "flip-flop" mechanism; the Pi binding in the active center exerts a strong influence on individual steps of the reaction.
D001665:Binding Sites; D043564:Inorganic Pyrophosphatase; D007527:Isoenzymes / Q000378:metabolism; D007700:Kinetics; D046911:Macromolecular Substances; D010766:Phosphorylation; D011485:Protein Binding; D011755:Pyrophosphatases / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology*
D007527:Isoenzymes; D046911:Macromolecular Substances; D011755:Pyrophosphatases; D043564:Inorganic Pyrophosphatase
Kooperativnyĭ mekhanizm fosforilirovaniia monomernoĭ i dimernoĭ form neorganicheskoĭ pirofosfatazy iz pekarskikh drozhzheĭ.