Characterization of the Membrane-bound Adenosine Triphosphatase from Corn Roots

옥수수 뿌리로부터 분리한 Membrane-bound ATPase의 특성에 관한 연구

The membrane-bound ATPases were separated on sucrose gradient from corn roots and characterized by pH optima, sensitivity to monovalent salt, Km and Vmax. The pH optima for the activity of all the ATPases associated with 13, 000g pellet and 13, 000~80, 000g pellet were 5 and 9, respectively. The ATPases in Fractions B and C of the 13, 000 g pellet were more active at pH 5 than pH 9. While, in the case of Fractions D, E and F, they were reverse. The activities of the ATPase in Fractions A and C of the 13, 000~80, 000 g pellet were greater at pH 5 than pH 9. On the other hand, the ATPases in Fractions B, D, E, and F were more active at pH 9 than pH 5. The optimum concentraction of ATP for the assay was about 3 to 5 mM. The Km's for the membrane-bound ATPases in 13, 000g pellet and in 13, 000~80, 000 g pellet were 0.25 mM. While Vmax values for 13, 000g pellet were from 8.0 to 12.5 $\mu$M Pi/mg protein/hr. according to pH values, those for 13, 000~80, 000 g pellet were from 35.7 to 55.6 $\mu$M Pi/mg protein/hr. Activities of the membrane-bound ATPases in both 13, 000 g pellet and 13, 000~80, 000 g pellet were stimulated with increasing the concentration of $K^+$.

옥수수 뿌리로부터 분리한 13,000g pellet과 13,000~80,000g pellet 내에 있는 membrane-bound ATPases의 특성을 구명하였다. 13,000g pellet과 13,000~80,000g pellet의 membrane-bound ATPases의 최적 pH는 5와 9였다. Discontinuous sucrose gradient centrifugation에 의한 13,000g pellet의 분획중 Fraction C는 pH 5에서, Fraction D, E 및 F는 pH 5에서보다 pH 9에서 더높은 활성을 나타냈다. 13,000~80,000g pellet의 분획에서 보면, Fraction A, C는 pH 9보다 pH 5에서, Fraction B, D, E 및 F는 pH 5보다 pH 9에서 더 높은 활성을 가겠다. pH 5와 pH 9에서 membrane-bound ATPases의 기질포화 농도는 3~5 mM이며 ATP에 대한 Km 값은 모두 0.25 mM이였다. Vmax 값은 8.0~55.6 $\mu$M Pi/mg membrane protein/hr의 범위에 있었다. Membrane-bound ATPase의 활성은 $K^+$ 이온에 의해 증가되었다.