  The nucleon decay is a significant phenomenon to verify grand unified
theories (GUTs). For the precise prediction of the nucleon lifetime induced by
the gauge bosons associated with the unified gauge group, it is important to
include the renormalization effects on the Wilson coefficients of the
dimension-six baryon number violating operators. In this study, we have derived
the threshold corrections to these coefficients at the one-loop level in the
minimal supersymmetric SU(5) GUT and the extended one with additional SU(5)
vector-like pairs. As a result, it is found that the nucleon decay rate is
enhanced about 5% in the minimal setup, and then the enhancement could become
smaller in the vector-like matter extensions.
