  We discuss the general method of the calculation of the nucleon matrix
elements of an operator associated with nonvalence quarks. The method is based
on the QCD sum rules and low energy theorems. As an application of these
considerations, we calculate the strange quark matrix element as well as the
momentum distribution of the strangeness in the nucleon. We also calculate the
singlet axial constant associated with $\eta'$ meson as well as an axial
constant associated with heavy quarks.
