Hydrolysis reactions are strongly affected by pH
Rate =   k0 [D]   +    kH [H3O+] [D]  + kOH [OH-] [D]
uncatalysed specific acid specific base
    catalysis     catalysis
kobs = k0 + kH [H3O+] + kOH [OH-]
The uncatalysed reaction involves water, so strictly:
 k0  = k0’  [H2O]