An ecto-enzyme of NAD glycohydrolase induced by retinoic acid in human leukemic HL-60 cells is attributed to the molecule of leukocyte cell surface antigen CD38 (Kontani, K., et al. (1993) J. Biol. Chem. 268, 16895-16898). The cell surface antigen has an amino acid sequence homologous to Aplysia ADP-ribosyl cyclase that catalyzes the conversion of NAD to cyclic ADP-ribose with a calcium-mobilizing activity. A putative hyaluronate (HA)-binding motif which has recently been identified in CD44 antigen existed in the extracellular domain and intracellular amino terminus of CD38 antigen, CD38 antigen was indeed capable of binding to HA in a manner dependent on ionic strength. By contrast, no binding activity was found in Aplysia ADP-ribosyl cyclase. Thus CD38 antigen, like CD43 antigen characterized as a HA-receptor (or binding) protein, may function as an adhesion molecule.