大腸菌K-12とそのL-form NC7の膜結合性ATPaseの性質

Membrane bound ATPase of L-form NC7 exhibited a pH optimum of ca. 9.0, and hydrolyzed selectively ATP with the Km value of 0.55 mM. ADP inhibited competitively the hydrolysis of ATP with the Ki value of 0.22 mM. Ca^<2+> and Mg^<2+> as divalent cation were required for the activation of this enzyme, and of these cations optimal molar ratio to ATP were 4 : 5 in calcium at pH 8.5 and about 2 : 5 in magnesium. In the presence of calcium, the enzyme was inhibited by increased concentration of monovalent cations, although in the presence of magnesium, the enzyme was relatively insensitive to their ions. Azide, PCMB and DCCD strongly inhibited the enzyme activity. The enzyme was labile under the temperature below 0-4℃, but addition of 20% methanol to the storage buffer prevented it from their inactivation. The enzyme was stable when it was preincubated below 60℃ for 5 mim. Membrane bound ATPase of L-form NC7 was essentially similar to that of wild type.