Answer
493.7 MeV
Work Step by Step
The minimum kinetic energy for the process results in the proton, the antiproton, and the newly-created $K^+K^-$ pair at rest.
In that case, the initial kinetic energy equals the rest mass energy of the $K^+K^-$ pair, which is 2(493.7MeV).
The proton and the antiproton each possess half of that kinetic energy, or 493.7 MeV apiece.
