[Immunochemical investigations on the gene expression of horse serum carboxylesterase (author's transl)].

Immunochemical and enzymatic analyses of horse serum carboxylesterase were carried out with respect to the existence of a silent gene. Sera with positive phenotypic expression of esterase, both heterozygotes and presumed homozygotes, were compared with:--sera with positive phenotypic expression but genotypically +/O;--sera with a negative phenotypic expression, i. e. genotypically O/O;--sera of natural +/O "hemi-zygotes": mules (donkey lacking the esterase);--positive sera heated at 60 degrees C;--positive sera after specific inhibition of enzymatic activity. Titration by immunocompetition has shown that sera phenotypically negative do not contain an immunologically active "dummy" protein; however, using a sensitive immunotitration (rocket immunoelectrophoresis), traces of active protein could be demonstrated. Sera of +/O genotypes, both horses and mules, contain approximatively half of esterase present in +/+ sera. Heating at 60 degrees destroys the antigenic properties of the esterase almost completely, while, on the contrary, a specific inhibition of enzymatic activity leaves the antigenic properties unaffected.