  We investigate unification constraints in the simplest renormalizable
non-supersymmetric SU(5) framework. We show that in the scenario where the
Higgs sector is composed of the 5, 24, and 45 dimensional representations the
proton could be practically stable. We accordingly demonstrate that of all the
SU(5) scenarios only the non-renormalizable one with the 5, 24, and 15
dimensional Higgs multiplets can be verify if low-energy supersymmetry is not
realized in Nature.
