Kinetic Studies of a (Na++ K++ Mg2+) ATPase in Sugar Beet Roots |
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Authors: | SYLVIA LINDBERG GUNNAR HANSSON ERS KYLIN |
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Affiliation: | Department of Botany, Faculty of Science, Hokkaido University, Sapporo, Japan |
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Abstract: | Kinetic studies of a microsomal, dithiotreitol treated, homogenate from sugar beet roots led to the following conclusions about its ATPase activity: (1) MgATP in complex appears to be the primary substrate for the reaction. The reciprocal equilibrium constant for the binding to the enzyme is estimated to be approximately 0.2 × 10?3M. (2) Free ATP acts as a competitive inhibitor of the MgATP. The binding constant is about twice as high as for MgATP. Consequently the enzyme has less affinity for ATP than for MgATP. (3) Free Mg2+ has little influence on the velocity, as the binding affinity of the enzyme for Mg2+ is almost negligible. |
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