The Substrate Specificity of Dynein from Tetrahymena Cilia

抄録

The substrate specificity of the 22S dynein ATPase from Tetrahymena cilia was investigated. The 22S dynein exhibited a high specificity for ATP in terms of both apparent K_m and V_max: naturally occurring nucleoside triphosphates other than ATP were hydrolyzed slowly with an apparent K_m of 0.25-1 mM, a sharp contrast to that of ATP hydrolysis (1-4 μM). Pyrophosphate was a poor inhibitor for the dynein ATPase, indicating weak affinity. Since dynein binds ATP tightly and hydrolyzes it at a high rate, a method to determine a trace amount of ATP in the presence of other nucleoside triphosphates has been developed by taking advantage of this enzymatic characteristic of dynein. The effect of P¹, P⁵-di(adenosine-5'-)- pentaphosphate (Ap₅A) on the 22S dynein ATPase was also investigated. Ap₅A acted as a weak competitive inhibitor of the ciliary 22S dynein ATPase and the non-linearity of the double-reciprocal plot of the ATPase was confirmed in the presence of Ap₅A.