Identification and characterization of a soluble form of the plasma cell membrane glycoprotein PC‐1 (5′‐nucleotide phosphodiesterase)

Abstract

PC‐1 is a membrane glycoprotein, found on the surface of plasma cells and a few types of non‐lymphoid cells, which has recently been found to have 5′‐nucleotide phosphodiesterase activity. In this paper, we demonstrate the existence of enzymically active water‐soluble forms of PC‐1 in ascites from plasmacytoma‐bearing mice, normal mouse serum, and in supernatants of cultured mouse plasmacytoma cells and mouse L cells transfected with a cDNA encoding the membrane form of PC‐1. The water‐soluble enzyme activity can be specifically immunoprecipitated by a monoclonal antibody to an allotypic determinant on the membrane form of PC‐1, and resides on a slightly smaller polypeptide than membrane PC‐..