  Using a generalized Rubinstein-Duke model we prove rigorously that kinematic
disorder leaves the prediction of standard reptation theory for the scaling of
the diffusion constant in the limit for long polymer chains $D \propto L^{-2}$
unaffected. Based on an analytical calculation as well as Monte Carlo
simulations we predict kinematic disorder to affect the center of mass
diffusion constant of an entangled polymer in the limit for long chains by the
same factor as single particle diffusion in a random barrier model.
