By ATP hydrolysis, I mean the chemical reaction: ATP + Water -> ADP + Pi. Focusing only on the reaction, this is a nucleophillic substitution reaction, most likely occuring in SN2 mechanism. But so far, I haven't found a single paper reporting the energy of activation of this reaction uncatalyzed. So, does anyone actually measured/estimated the activation energy of uncatalyzed ATP hydrolysis reaction?
The activation energy of ATP hydrolysis at in the pH range 3–9 was determined by Kahn and Mohan in 1974 and found to be 28.0 to 20.7 kcal/mole. At neutrality (i.e. uncatalysed) it would appear to be:
approx. 23 kcal/mole
A subscription is required to access the paper, but I reproduce the key table as fair citation under copyright laws:
I imagine that redeterminations or confirmations have been performed more recently and can be found by searching the chemical, rather than biological, literature. (And @Chris would seem to have confirmed this in his answer.)
The 2014 paper of Wang and colleagues found the activation energy of ATP at 32.5 kcal/mol. See the reference for details. The image is figure 3 from the reference.