Human CD38, a surface receptor, an enzyme, an adhesion molecule and not a simple marker

Human CD38 is a 45 kDa type II trans-membrane glycoprotein with a peculiar discontinuous pattern of expression in leukocytes, although evidence is acc umulating of its quite widespread expression outside of the hematopoietic s ystem. CD38 is a member of an emerging family of cytosolic and membrane-bou nd enzymes whose substrate is nicotinamide adenine dinucleotide (NAD), a co enzyme ubiquitously distributed in nature. CD38 is a multifunctional molecu le able to exert not only an enzymatic activity but also to mobilize calciu m, to transduce signals, to adhere to hyaluronan and to other ligands. Inte raction with CD38 on various leukocyte subpopulation has profound though di verse effects on their life-span, however, the immunoregulatory activities seem to be independent of the enzymatic functions of the molecule.