Nicotinamide adenine dinucleotide: beyond a redox coenzyme

ADP- ribosylation using nicotinamide adenine dinucleotide ( NAD+) is an important type of enzymatic reaction that affects many biological processes. A brief introductory review is given here to various ADP- ribosyltransferases, including poly( ADP- ribose) polymerase ( PARPs), mono( ADP- ribosyl)-transferases ( ARTs), NAD(+)- dependent deacetylases ( sirtuins), tRNA 2- phosphotransferases, and ADP- ribosyl cyclases ( CD38 and CD157). Focus is given to the enzymatic reactions, mechanisms, structures, and biological functions.