  We examine proton decay mediated by color-triplet Higgsinos in minimal
supersymmetric $SU(5)$ grand unified theory in light of the discovery of the
Higgs boson and the absence of SUSY signals at the LHC. We pay special
attention to various threshold effects arising from Planck-suppressed operators
that affect the color-triplet Higgsino mass and also correct the wrong mass
relations for the light fermions. Our analysis allows for a non-universal SUSY
spectrum with the third family scalars having a separate mass compared to the
first two families. We identify the allowed parameter space of the model and
show that the SUSY scalar masses are constrained by current limits from proton
lifetime to be above 5 TeV, while the glunio, Wino and the Higgsinos may be
within reach of the LHC. When the SUSY scalar masses are required to be $\leq
20$ TeV, so that they are within reach of next generation collider experiments,
we find that proton lifetime for the decay $p \rightarrow \overline{\nu} K^+$
is bounded by $\tau(p \rightarrow \overline{\nu} K^+) \leq 1.1 \times 10^{35}$
yrs.
