[Kinetic interpretation of the original pH-dependence of enzymatic activity of "basal" Mg(2+)-ATPase of the smooth muscle sarcolemma].

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  • Additional Information
    • Source:
      Publisher: Nat︠s︡ionalʹna akademii︠a︡ nauk Ukraïny, Instytut biokhimiï im. O.V. Palladina Country of Publication: Ukraine NLM ID: 101657175 Publication Model: Print Cited Medium: Print NLM ISO Abbreviation: Ukr Biokhim Zh (1999) Subsets: MEDLINE
    • Publication Information:
      Original Publication: Kyïv : Nat︠s︡ionalʹna akademii︠a︡ nauk Ukraïny, Instytut biokhimiï im. O.V. Palladina, 1999-2013.
    • Subject Terms:
      Ca(2+) Mg(2+)-ATPase/*metabolism ; Myometrium/*enzymology ; Sarcolemma/*enzymology; Adenosine Triphosphate/metabolism ; Animals ; Female ; Hydrogen-Ion Concentration ; In Vitro Techniques ; Kinetics ; Models, Biological ; Myometrium/cytology ; Protons ; Swine
    • Abstract:
      It was demonstrated in experiments made on a fraction of plasma membranes of the uterine smooth muscle cells that PH-dependence of enzymatic activity of the "basal" (Ca(2+)-independent) Mg(2+)-ATPase obtained under the conditions of determining the initial velocity of ATP hydrolysate is not bell-shaped but is characterized by linearity in the range of the values of hydrogen index 6.0-8.0. A kinetic model of Mg(2+)-dependent enzymatic hydrolysis of ATP has been suggested and analyzed; the model explains the linearity of the above pH-dependence. Results of kinetic analysis prove that the cause of linear pH-dependence of enzymatic activity of the "basal" Mg(2+)-ATPase is that the proton H+ is a competitive inhibitor of the given enzyme: the increase of protons concentration leads to a decrease of the affinity of Mg(2+)-ATP substrate for the enzyme, but it has no effect on the number of circulations of the latter. Thus the work gives a kinetic substantiation of the possible regulatory role of protons H+ as the factor of original negative inverse relation which controls the enzymatic activity of the basal Mg(2+)-ATPase "producing" protons in the myometrium cells; the concentration of protons in the near-membrane regions of the myoplasma being increased the ATPase activity decreases, and the former being decreased the latter increases. It is not excluded that owing to its original linear pH-dependence the studied ATP-hydrolase system serves as an important element of the control of proton homeostasis in the smooth-muscle cells.
    • Accession Number:
      0 (Protons)
      8L70Q75FXE (Adenosine Triphosphate)
      EC 3.6.1.- (Ca(2+) Mg(2+)-ATPase)
    • Publication Date:
      Date Created: 20090722 Date Completed: 20090821 Latest Revision: 20150803
    • Publication Date:
      20231215
    • Accession Number:
      19618740