Further studies on the chemical basis for serological specificity of Group A streptococcal carbohydrate.

Azoproteins prepared with p-aminophenyl-beta-N-acetyl-glucosaminide react in precipitin tests with Group A streptococcal antisera. The reaction is nonreciprocal, and antisera to the azoprotein do not react with Group A carbohydrate. Phenyl-N-acetyl-glucosaminides inhibit the reaction of Group A carbohydrate with homologous antisera and with antisera to the azoprotein. The beta-anomer is more effective as an inhibitor than the alpha-anomer. Formation by a soil bacillus of the enzyme which removes N-acetyl-glucosamine from Group A carbohydrate is induced by phenyl-beta-N-acetyl-glucosaminide but not by the alpha-compound. The enzyme, like the glucosaminidase of emulsin, appears to be specific for beta-glucosaminides. Neither the induced enzyme nor emulsin effectively remove all of the N-acetyl-glucosamine from the azoprotein antigens. The findings support the view that beta-N-acetyl-glucosaminide side chains represent the major antigenic determinant of Group A streptococcal carbohydrate.