STUDIES OF N-LINKED OLIGOSACCHARIDE CHAINS OF ALPHA(1)-ACID GLYCOPROTEIN ISOLATED FROM ASCITIC FLUID OF STOMACH-CANCER PATIENTS AND NORMAL SERUM

Human alpha1-acid glycoprotein (AGP) with apparent molecular weight 44 kDa was isolated from normal human serum (n-AGP and ascitic fluid, of patients with stomach cancer (a-AGP), Both AGPs yielded single bands in SDS-electrophoresis and immunodiffusion. Aminoacid compositions of both AGPs were similar, but carbohydrate ones were different as well a s their affinity to Con A. A comparative study of the structure of alp ha-AGP and n-AGP N-glycans was carried out by HPLC analysis with two t ypes of column's (OS-mapping) in the combination with their sequential exoglycosidase digestion. N-glycans were released by hydrazinolysis o r by treatment with LiBH4 - LiOH - tert-BuOH and subjected to reductiv e amination with a fluorescent reagent, 7-amino-4-methylcoumarine (AMC ) in the presence of LiBH3CN. The mixture of labeled OSs obtained (AMC -OS) was analysed by HPLC; n-AGP and alpha-AGP had identical glycan co mposition but the amounts of biantennary glycans, agalacto-oligosaccha rides as well as the content of Le(x)-fragments in a-AGP were increase d.