Removal of O-acetylated sialic acids from rat colonic epithelial glycoproteins by cell-free extracts of rat faeces.

Sterile, cell-free, extracts of freshly defaecated Wistar rat faeces in a pH 7.0 "minimal medium" contain neuraminidase(s), capable of removing sialic acids both with and without side-chain substituents from bovine submandibular mucin and rat colonic epithelial glycoproteins, and an esterase which removes O-acetyl substituents from the side chain of sialic acid residues. Studies of the removal of sialic acids from bovine submandibular mucin and rat colonic epithelial glycoproteins indicated that (i) the faecal enzymes removed a greater proportion of the sialic acid of both the de-O-acetylated and native glycoproteins than was removed with Vibrio cholera neuraminidase, (ii) sialic acids were removed more rapidly from de-O-acetylated glycoproteins, and (iii) the resistance to removal of sialic acids was apparently dependent at least in part upon the O-acetyl sialic acid content of the substrate.