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.