BLOOD GROUP ANTIGENS 



91 



of A, B, and H substances. As expected, the destructive action of 

 the enzyme preparation on A substance was inhibited by A^-acetyl- 

 galactosamine, the action on B substance by galactose, and the action 

 on H substance by fucose. 



There is at present no clue to the identity of the monosaccharide 

 unit next to fucose in the specific part of the H substance. Our best 

 picture of its structure is shown in Fig. 7-7 , where x stands for a 

 number of the order of five. 



H Substance 



X = approx. 5 

 Fig. 1-1 . Suggested structure of blood group H substance. 



Watkins and Morgan (1957) found that the destruction of the 

 serological activity of the Le"* antigen by the Trichomonas enzymes was 

 inhibited by L-fucose, which suggested a role for this sugar in the 

 specificity of the Le"* antigen. However, the agglutination of Le(a+) 



H 



Q^ ,. NHCOCH3 



-[i - D - A/- AcetylglucosaminoyI ■ 



' ^ \r 



H\OH h/h 



H OH 



/9-D-GalQCtosyl - 



Fig. 7-8. Suggested structure of terminal portion of blood group Le^ sub- 

 stance (Morgan and Watkins, 1959). 



