Aminotransferases (ATs) had previously been detected after native electrophoresis. We show now that aminotransferase(s) of Propionibacterium freudenreichii can be detected after sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). Moreover, it retained a high activity (84%) in the presence of 0.23% SDS, contrary to what was observed for aminotransferase(s) of Bifidobacterium bifidum (54%) and of six other cheese-related species (0-20%).