Combining Medium Effects and Cofactor Catalysis: Metal‐Coordinated Synzymes Accelerate Phosphate Transfer by 108

The systematic exploration of the modification of polyethylene imine with guanidinium and octyl groups has led to the identification of a catalyst, CD6, which accelerates the phosphate transfer reaction of HPNP (2‐hydroxypropyl‐4‐nitrophenyl phosphate) in the presence of divalent metals such as Zn²⁺, Co²⁺, Mg²⁺ or Ni²⁺. CD6 exhibits saturation kinetics that are described by Michaelis–Menten parameters K_m ranging from 2.5–8 mM and k_cat ranging from 0.0014–0.09 s^?1. For Zn^II–CD6 this corresponds to an overall acceleration k_cat/k_uncat of 3.8×10⁵ and a catalytic proficiency (k_cat/K_m)/k_uncat of 1.5×10⁸. Catalysis by Zn^II–CD6 is specifically inhibited by inorganic phosphate, allowing turnover regulation by product inhibition. This effect stands in contrast to Zn^II‐catalysed transesterification of HPNP in water or by the synzymes Co^II–CD6 and Ni^II–CD6, with which no such interference by product is observed. These characteristics render synzyme Zn^II–CD6 an efficient enzyme model that reflects enzyme‐like properties in a wide range of features.