Immune properties of glucosyltransferases from S. sobrinus

GTF activity was separated into water‐insoluble (GTF‐I) and water‐soluble (GTF‐S) polyglucan‐synthesizing enzymes. Each preparation demonstrated a single band on 6% SDS PAGE. Only water‐insoluble or water‐soluble polyglucan was synthesized by the respective enzyme preparation. Rats were immunized, on Days 1 and 14, with either GTF‐I or GTF‐S in adjuvant. Animals were bled 13, 35 and 54 days after the initial immunization. Individual antisera were tested against either the GTF‐I or the GTF‐S for inhibition of radioactive glucose incorporation into glucan, and in gel diffusion, and by Western transfer analyses. The respective antisera reacted with the homologous, but not the heterologous enzyme in gel diffusion and Western transfer. GTF‐I activity was not inhibited by antibody to GTF‐S, but antibody to GTF‐I inhibited GTF‐I by 68%. GTF‐S was inhibited by more than 60% by each of 3 anti‐GTF‐S sera. Only one anti‐GTF‐I serum inhibited GTF‐S at as much as a modest 30% level. These data support the antigenic and functional distinctiveness of the GTF enzymes of S. sobrinus 6715.