GCAP-II - ISOLATION AND CHARACTERIZATION OF THE CIRCULATING FORM OF HUMAN UROGUANYLIN

The systematic isolation of circulating regulatory peptides which gene rate cGMP as second messenger resulted in the identification of a nove l member of the guanylin family. In the present study we describe the purification and amino acid sequence of a new guanylate cyclase C acti vating peptide (GCAP-II), GCAP-II contains 24 amino acids in the follo wing sequence: FKTLRTIANDDCELCVACTGCL. Its molecular mass is 2597.7 Da , The 16 C-terminal amino acids are identical to uroguanylin from huma n urine, Native and synthetic GCAP-II activate GC-C, the specific guan ylate cyclase receptor, of cultured human colon carcinoma (T84) cells, GCAP-II stimulates chloride secretion in isolated human intestinal mu cosa mediated by intracellular cGMP increase, GCAP-II specific antibod ies were used to localize the peptide by immunohistochemistry in enter o-endocrine cells of the colonic mucosa.