Kinetic properties of mitochondrial H+-adenosine triphosphatase in Morris hepatoma 3924A.

A study of kinetic properties of mitochondrial ATPase in Morris hepatoma 3924A is reported. The results show that submitochondrial particles isolated from the tumor tissue exhibited a three-fold increase in both the Km for ATP hydrolysis and Ki for the competitive inhibitor [beta, gamma-imido]ATP with regard to normal rat liver. Eadie-Hofstee analysis of the kinetics of ATP hydrolysis show that both the high and the low affinity constants for ATP were enhanced in the hepatoma with respect to the rat liver enzyme. Kinetic analysis of passive proton conduction through the F0 sector of ATPase does not reveal any difference between Morris hepatoma and rat liver. In Morris hepatoma particles, 50% inhibition of the hydrolase activity required 10 times more oligomycin than in control particles. On the contrary, 50% inhibition of proton conduction occurred in both hepatoma and rat liver particles at the same concentration of oligomycin. It is concluded that in Morris hepatoma the catalytic process in F1 and the functional connection between F1 and F0 of the ATP synthase are altered with regard to control rat liver.