CYCLIC ADP-RIBOSE - A NEW COMPONENT OF CALCIUM SIGNALING

Cyclic ADP-ribose is a recently discovered metabolite of NAD that appe ars to function in cellular calcium signaling. The discovery that NAD glycohydrolases are bifunctional enzymes that catalyze both the synthe sis and hydrolysis of cyclic ADP-ribose raises many questions concerni ng the mechanisms by which these enzymes function in calcium signaling . Likewise, the identification of human lymphocyte antigen CD 38 as a bifunctional NAD glycohydrolase raises interesting questions concernin g the involvement of cyclic ADP-ribose mediated calcium signaling in i mmune function. The dementia associated with niacin deficiency has bee n a long-standing curiosity. This signaling mechanism may resolve ques tions connecting this vitamin deficiency to central nervous system (CN S) function.