A revised structure for the Forssman glycolipid hapten.

A glycolipid hapten of the Forssman antigen of horse spleen was found to be a ceramide pentasaccharide, which contained 2 moles of N-acetylgalactosamine, 2 moles of galactose, and 1 mole of glucose per ceramide. An ar-N-acetylgalactosaminidase of hog liver (WEISSMAN, B., AND HINRICHSEN, D. F., Biochemistry, 8, 2034 (1969)) hydrolyzed the terminal a-N-acetylgalactosaminosyl residue with a simultaneous loss of the Forssman hapten activity. The resulting compound was identical with globoside (YAMAKAWA, T., NISHIMURA, S., AND KAMIMURA, H., J@. J. Exp. Med., 35, 201 (1965) ; HAKOMORI, S., SIDDIQUI, B., LI, Y. T., LI, S. C., AND HELLERQVIST, C. G., J. Bi02. Chem. 246,227l (1971)) and gave a specific precipitin reaction with anti-globoside antiserum. The oligosaccharide released from the Forssman hapten gave an intense Morgan-Elson reaction and 1 of the 2 moles of galactosamine was periodate resistant. With these results and those of methylation studies, the structure of Forssman hapten was proposed as N-acetylgalactosaminosyl-a-(1 -+ 3) N-acetylgalactosaminosyl-P-(1 + 3)galactopyranosyl-c-(1 -+ 4)galactopyranosyl+(l --f 4)glucopyranosyl-(1 -+ l)ceramide.