Facile chemoenzymatic synthesis of a novel stable mimic of NAD

Nicotinamide adenine dinucleotide (NAD⁺) is an essential cofactor participating in a variety of important enzyme-catalyzed physiological and pathophysiological processes. Analogues of NAD⁺ provide key and valuable agents for investigating NAD⁺-dependent enzymes. In this study, we report the preparation of a novel stable NAD⁺ mimic, 4'-thioribose NAD⁺ (S-NAD⁺), using a facile and efficient chemoenzymatic approach. Substrate activity assays indicated the resulting S-NAD⁺ is chemically inert to human CD38 and sirtuin 2 enzymes, but capable of participating in redox reactions in a manner similar to NAD⁺. X-ray crystallographic analysis revealed binding of S-NAD⁺ to the active site of human CD38 and critical residues involved in leaving group activation and catalysis. By more closely mimicking NAD⁺ in geometry and electrostatics, the generated S-NAD⁺ offers a unique and important tool that can be extended to study enzymes utilizing NAD⁺.