(A) Proton transfer, decarboxylation and hydride transfer reactions of whole substrates (k_cat/K_m) and the substrate fragments (k_cat/K_HPiK_d) catalyzed by TIM, OMPDC, and GPDH, respectively. ‘Rx’ and ‘Px’ denote reactant and product states, respectively. The phosphoryl group of each whole substrate provides a total 11–13 kcal·mol⁻¹ stabilization of the transition states for the catalyzed reaction, while 1.0 M phosphite dianion provides a 6–8 kcal·mol⁻¹ stabilization of the transition states for the catalysis of each truncated substrate fragment [13]. (B) Dianion activators of the reactions of the substrate fragments [10]. (C) The model developed to rationalize activation of TIM, OMPDC and GPDH.