Double-Electron Reduced Diphenylviologen as a Coenzyme for Biocatalytic Building Carbon-Carbon Bonds from CO2 as a Carbon Feedstock

Malate dehydrogenase (oxaloacetate-decarboxylating) commonly named malic enzyme (ME) from chicken liver (EC 1.1.1.40) catalyzes a reaction introducing CO2 as a carboxy-group to pyruvate to form malate via oxaloacetate in the presence of the coenzyme NADPH, and is an attractive biocatalyst for building C-C bonds using CO2 as a chemical carbon feedstock. We previously discovered that multielectron reduced diphenylviologen derivatives (PVs) can act as an artificial coenzyme for ME, replacing the expensive NADPH (natural coenzyme), in the formation of malate. In this Letter, the kinetic parameters of oxaloacetate production based on building C-C bonds of a coupling pyruvate and CO2 with water-soluble PVs, double electron reduced 1,1'-bis(p-carboxyphenyl)-4,4'-bipyridinium dichloride (PCV degrees) and ME were determined with the analysis of enzymatic kinetics for the first time. PCV degrees acts as a Lewis base and is involved in oxaloacetate production via C-H bond activation and carboxylation of pyruvate by CO2.