Cell-surface peptidases as modulators of growth and differentiation.

Some of the many cell-surface antigens defined by the CD (cluster differentiation) nomenclature have lately emerged as proteins with well-characterised enzymic activities. One important example is CD10 or CALLA (common acute lymphoblastic leukaemia antigen), which is identical to endopeptidase-24.11, an enzyme with an important role in the hydrolysis of biologically active peptides. CD13 and CD26 are also surface peptidases. These enzymes, which have a wide distribution on the surfaces of various cell types, may have specific roles in the control of growth and differentiation in both haemopoietic and epithelial cell systems.