This introductory chapter briefly reviews the history, chemistry, and biochemistry of NAD (the term NAD as it is used here refers to both oxidized and reduced forms of the molecule) consuming ADP-ribose transfer enzymes as components of the involvement of vitamin B3 in health and disease.
Keywords: ADP-ribose; Nicotinamide; Nicotinamide riboside; Nicotinic acid; Pellagra; Vitamin B3.