title: [Features of the effect of ammonium ion on the enzymatic activity of myosin and subfragment-1].
abstract: The kinetic isotope effect of hydrolysis of ATP by myosin subfragment-I in the presence of K+, NH4+, Rb+ was measured. VH/VD was found to be 1.8; 1.3; 2.0, respectively. According to the thermodynamic isotope effect induced by hydration, the kinetic isotope effect must increase with the increase of cation size from K+ to Rb+. The size of ammonium ions is the intermediate between K+ and Rb+, but the observed isotope effect in the presence of ammonium is much lower than in the presence of K+ and Rb+. The results suggest that monovalent cations occur near the active center of the enzyme and contribute to some extent to the hydrolysis reaction but the specificity of ammonium ions seems not to be due to its ideal steric accordance. The obtained results support the viewpoint that NH4+ ions as donor of protons participate in the chemical stage of ATP hydrolysis by subfragment-I.
authors: V I
authors: VI
authors: Lobyshev
authors: Z I
authors: ZI
authors: Vishnevskaia
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000641:Ammonia / Q000737:chemistry*; D006868:Hydrolysis; D007554:Isotopes; D007700:Kinetics; D015879:Myosin Subfragments / Q000378:metabolism*; D009218:Myosins / Q000378:metabolism*; D013816:Thermodynamics
chemical_list: D007554:Isotopes; D015879:Myosin Subfragments; D000641:Ammonia; D000255:Adenosine Triphosphate; D009218:Myosins
vernacular_title: Osobennosti vliianiia iona ammoniia na fermentativnuiu aktivnost' miozina i subfragmenta-1.