This is unique to the best of our knowledge, and provides a direct linkage between loop dynamics and the chemical steps of catalysis in PTPs. The work reported here is part of our broader efforts to understand factors affecting WPD-loop dynamics in the PTP family. Only the three WPD residues are highly conserved within the ~12-residues comprising this loop. To explore the role of non-conserved residues in the WPD-loop on catalysis and pH dependency, we have created and characterized a series of loop-swapped chimeras. In a previous report, we described chimeras in which the WPD-loop of PTP1B was exchanged into YopH, which resulted in unexpected and counterintuitive kinetic and structural results. Here, we report the characterization of reverse chimeras, based on the transposition of the faster, YopH enzyme loop into the slower enzyme, PTP1B. We began with a chimera consisting of the full YopH WPD-loop transposed into PTP1B, followed by a stepwise mutation back toward the native PTP1B loop sequence. Not all of the chimeras proved to be soluble and amenable for study, and we include those findings in the interest of including negative results. For the soluble, active Chimeras, enzymatic functions were examined by steady-state kinetics to obtain kcat values, and kinetic isotope effects with the substrate pNPP, which report on transition state details of the first step of catalysis. Degradation in the correct positioning of the Asp residue due to an altered WPD-loop conformation will affect the coordination of leaving group protonation with P-O bond fission in the first step of catalysis, and its role as a general base in the second step.