In this paper using a transform defined by the translation operator we introduce the concept of spectrum of sequences that are bounded by n ν , where ν is a natural number. We apply this spectral theory to study the asymptotic behavior of solutions of fractional difference equations of the form ∆ α x(n) = T x(n) + y(n), n ∈ N, where 0 < α ≤ 1. One of the obtained results is an extension of a famous Katznelson-Tzafriri Theorem, saying that if the αresolvent operator Sα satisfies sup n∈N Sα(n) /n ν < ∞ and the set of z 0 ∈ C such that (z − kα (z)T ) −1 exists, and together with kα (z), is holomorphic in a neighborhood of z 0 consists of at most 1, where kα (z) is the Z-transform of