Thiamine diphosphate-dependent enzymes: mechanistic principles, stereoselective C-C bond formation, and synthetic...

Over the past several decades, biocatalysis has become a valuable complement to synthetic chemistry due to its high efficiency, exceptional selectivity, and environmental compatibility. Thiamine diphosphate (ThDP), the biologically active form of vitamin B1, serves as an essential coenzyme for core metabolic processes in all organisms. This review systematically elucidates the structural characteristics, classification, and diverse reactions catalyzed by ThDP-dependent enzymes, with a primary focus on their potential for stereoselective C-C bond formation and cleavage. These enzymes are widely distributed across all domains of life and catalyze the formation and cleavage of C-C, C-N, C-S, and C-O bonds. The catalytic mechanism centers on the formation of the Breslow intermediate, which undergoes nucleophilic addition to various electrophiles. Despite considerable sequence diversity, all ThDP-dependent enzymes share two conserved domains-the pyrimidine (PYR) binding domain and the pyrophosphate (PP) binding domain-and are classified into five structural types and nine superfamilies. In terms of substrate scope, the decarboxylase family is predominantly R-selective, whereas the transketolase family is S-selective. These enzymes hold significant promise for biotechnological applications, particularly through protein engineering to tailor catalytic activity and stereoselectivity. Moreover, ThDP-dependent enzymes have been implicated in the pathogenesis of Alzheimer's disease, diabetes, and tumor proliferation. This review also summarizes relevant clinical applications and the use of competitive inhibitors. By integrating modular architectures, cofactor synergy mechanisms, regulatory networks, and emerging frontiers in photoelectrochemical biocatalysis, this review highlights the broad potential of ThDP-dependent enzymes in both fundamental research and translational applications.