  In grand unified theories based on orbifold constructions in higher
dimensions, Higgsino-mediated proton decay is absent. However, proton decay
mediated by $X$ and $Y$ gauge bosons is typically enhanced to levels detectable
by current and future experiments. We analyse the phenomenology of proton decay
induced by the minimal coupling of $X,Y$ gauge bosons. In particular, we show
that the novel realization of matter in orbifold GUTs can lead to unusual final
state flavour structure, for example, the dominance of the $p\to K^0\mu^+$
mode. Furthermore, we discuss proton decay induced by higher-derivative brane
operators, finding potentially observable rates for natural values of the
operator coefficients.
