FORMATION AND HYDROLYSIS OF CYCLIC ADP RIBOSE CATALYZED BY LYMPHOCYTEANTIGEN-CD38

CD38 is a 42-kilodalton glycoprotein expressed extensively on B and T lymphocytes. CD38 exhibits a structural homology to Aplysia adenosine diphosphate (ADP)-ribosyl cyclase. This enzyme catalyzes the synthesis of cyclic ADP-ribose (cADPR), a metabolite of nicotinamide adenine di nucleotide (NAD+) with calcium-mobilizing activity. A complementary DN A encoding the extracellular domain of murine CD38 was constructed and expressed, and the resultant recombinant soluble CD38 was purified to homogeneity. Soluble CD38 catalyzed the formation and hydrolysis of c ADPR when added to NAD+. Purified cADPR augmented the proliferative re sponse of activated murine B cells, potentially implicating the enzyma tic activity of CD38 in lymphocyte function.