CD38 (ADP-ribosyl cyclase/cyclic ADP-ribose hydrolase 1) is a type II transmembrane glycoprotein that synthesizes and hydrolyzes cyclic adenosine 5'-diphosphate-ribose, an intracellular calcium ion mobilizing messenger. The release of soluble protein and the ability of membrane-bound protein to become internalized indicate both extracellular and intracellular functions for the protein. The functional CD38 molecule is a dimer, with the central portion containing the catalytic site. CD38 is used as a prognostic marker for patients with chronic lymphocytic leukemia. Alternative splicing results in multiple transcript variants. [taken from NCBI Entrez Gene (Gene ID: 952)].