  We study the operator product algebra of the supercurrent J and Konishi
superfield K in four-dimensional supersymmetric gauge theories. The Konishi
superfield appears in the JJ OPE and the algebra is characterized by two
central charges c and c' and an anomalous dimension h for K. In free field
(one-loop) approximation, c~3N_v+N_\chi and c'~N_\chi, where N_v and N_\chi
are, respectively, the number of vector and chiral multiplets in the theory. In
higher order c, c' and h depend on the gauge and Yukawa couplings and we obtain
the two-loop contributions by combining earlier work on c with our own
calculations of c'. The major result is that the radiative corrections to the
central charges cancel when the one-loop beta-functions vanish, suggesting that
c and c' (but not h) are invariant under continuous deformations of
superconformal theories. The behavior of c and c' along renormalization group
flows is studied from the viewpoint of a c-theorem.
