Chemo-enzymatic synthesis of isotopically labeled nicotinamide ribosideElectronic supplementary information (ESI) available. See DOI: 10.1039/c8ob00552d

As a cofactor for numerous reactions, NAD + is found widely dispersed across many maps of cellular metabolism. This core redox role alone makes the biosynthesis of NAD + of great interest. Recent studies have revealed new biological roles for NAD + as a substrate for diverse enzymes that regulate a broad spectrum of key cellular tasks. These NAD + -consuming enzymes further highlight the importance of understanding NAD + biosynthetic pathways. In this study, we developed a chemo-enzymatic synthesis of isotopically labeled NAD + precursor, nicotinamide riboside (NR). The synthesis of NR isotopomers allowed us to unambiguously determine that NR is efficiently converted to NAD + in the cellular environment independent of degradation to nicotinamide, and it is incorporated into NAD + in its intact form. The versatile synthetic method along with the isotopically labeled NRs will provide powerful tools to further decipher the important yet complicated NAD + metabolism. A versatile chemo-enzymatic synthesis of isotopically labeled nicotinamide riboside (NR) was developed.