  We study the small-$x$ evolution equation for the gluon generalized parton
distribution (GPD) $E_g$ of the nucleon. It is shown that $E_g$ at vanishing
skewness exhibits the Regge behavior identical to the BFKL Pomeron, despite its
association with nucleon helicity-flip processes. We also consider the effect
of gluon saturation and demonstrate that $E_g$ gets saturated in the same way
as its helicity-nonflip counterpart $H_g$. Our result has a direct impact on
the modeling of $E_g$ as well as the small-$x$ contribution to nucleon spin sum
rules.
