The rate constant for the uncatalyzed reaction of two molecules of glycine ethyl ester to form glycylglycine ethyl ester is 0.6 s^-1 M^-1. In the presence of [Co(ethylenediamine)₂]²⁺, the rate constant is 1.5 × 10⁶ s^-1 M^-1. What rate enhancement does the catalyst provide?