  Properties of the nucleon twist-3 distribution function e(x) are reviewed. It
is emphasized that the QCD equations of motion imply the existence of a
delta-function at x=0 in e(x), which gives rise to the pion-nucleon sigma-term.
According to the resulting ``practical'' DIS sum rules the first and the second
moment of e(x) vanish, a situation analogue to that of the pure twist-3
distribution function $\bar{g}_2(x)$.
