title: Expression of an active proteinase inhibitor, alpha 1-antichymotrypsin, by human breast epithelial cells.
abstract: The synthesis of an active proteinase inhibitor, gp 66, by human breast epithelial cells is reported. This glycoprotein is identical to serum alpha 1-antichymotrypsin, which inhibits proteinases that cleave at hydrophobic residues. Immunohistological studies show the in vivo expression on normal secretory and ductal epithelial cells and on primary and metastatic adenocarcinomas. Immunoaffinity-purified gp 66 from MCF-7 culture supernatants is an active inhibitor of chymotrypsin as determined in a fluorogenic enzyme assay and can form stable 88 kDa enzyme-inhibitor complexes. The synthesis of a functional inhibitor may represent the epithelial cell's attempt to stabilize its extracellular milieu.
mesh_terms: D001940:Breast / Q000201:enzymology*; D001943:Breast Neoplasms / Q000201:enzymology*; D002448:Cell Adhesion; D002460:Cell Line; D002918:Chymotrypsin / Q000037:antagonists & inhibitors* / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism; D004848:Epithelium / Q000201:enzymology; D005260:Female; D005455:Fluorescent Antibody Technique; D006023:Glycoproteins / Q000032:analysis; D006801:Humans; D007526:Isoelectric Point; D008970:Molecular Weight; D000514:alpha 1-Antichymotrypsin
chemical_list: D006023:Glycoproteins; D000514:alpha 1-Antichymotrypsin; D002918:Chymotrypsin