Title : Structural studies on oncofetal carbohydrate antigens (Ca 19-9, Ca 50, and Ca 125 ) carried by O-linked sialyloligosaccharides on human amniotic mucins
Abstract :
Mucins were extracted from human amniotic fluid in the presence of 45 % vol
phenol and separated from the bulk of smaller-sized glycoproteins by exclusion on Sephacryl S400
The mucin-fraction FW, which still contained a minute proportion of mannose, strongly expressed oncofetal antigens recognized by monoclonal antibodies C 50, NS 19-9, OC 125, Leu M1, 49 H 8, and 115 C 2
The structures of the respective mucin-linked saccharides responsible for Ca 50-, Ca 19-9-, and Lea-related antigenic activities were analyzed before or after reductive beta-elimination from sialylglycoproteins , and purification of the derived alditols by gel-permeation chromatography on Bio-Gel P-4 or high performance liquid chromatography
Two ubiquitous (FW2, FW3) and three novel oligosaccharide alditols (FW5) were characterized by f.a.b.- and e.i.-m.s., combined with methylation analysis and chromium trioxide oxidation
The OC 125 epitope on mucin-carried O-glycans was destroyed during reductive cleavage of the saccharides , indicating a conformational involvement of the reducing terminal residue and its mode of conjugation to the protein
Exoglycosidase treatment of the mucin-bound antigen revealed that the epitope structure of OC 125 includes terminal beta-D-galactosyl groups, and terminal sialyl groups that are almost inaccessible to Vibrio cholerae sialidase digestion