Pheromaxein, the pheromonal steroid-binding protein, is a major protein synthesized in porcine submaxillary salivary glands.

Submaxillary salivary gland tissue from large White, Göttingen miniature and Meishan (Chinese) breeds of pig, and European wild boars, was incubated with [35S]methionine. The radiolabelled amino acid was incorporated into protein in all incubations as demonstrated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). Specifically [35S]methionine was predominantly incorporated into the alpha- and beta-charge isomers of pheromaxein, a 16-androstene steroid-binding protein, as shown by SDS-PAGE in combination with vertical isoelectric focusing on polyacrylamide slab gels. The synthesis of pheromaxein occurred in submaxillary gland tissue from both sexes, including tissues stored frozen at -70 degrees C for long periods. There was little evidence for pheromaxein synthesis in parotid gland tissue or skeletal muscle. Total protein, pheromaxein and total 16-androstenes were determined in the submaxillary gland cytosols of six mature Göttingen miniature boars and a positive correlation was found between these glandular constituents. The amounts of endogenous pheromaxein relative to total protein in the submaxillary gland cytosols (range 10.3-18.0%), together with the predominant synthesis of this protein in vitro, indicate that pheromaxein is a major protein produced in porcine submaxillary glands, particularly in those of the male.