THE ROLES OF ENTERIC BACTERIAL SIALIDASE, SIALATE O-ACETYL ESTERASE AND GLYCOSULFATASE IN THE DEGRADATION OF HUMAN COLONIC MUCIN

Sialidase activity in normal faecal extracts showed a preference for m ucin-related glycoprotein and oligosaccharide substrates, but the pres ence of two or more O-acetyl esters at positions C-7-C-9 on the sialic acids retarded the rate of hydrolysis. A specific sialate O-acetyl es terase was detected with a lower total activity relative to sialidase with mucin substrates and having a pH optimum of 7.8 and a K(M) of app roximately 1 mM sialate O-acetyl ester. A specific glycosulfatase acti vity was found in faecal extracts using the substrate lactit-[H-3]ol 6 -O-sulfate with a pH optimum of pH 5.0 and a K(M) of approximately 1 m M. Faecal extracts from ulcerative colitis (UC) patients had higher si alate O-acetyl esterase and glycosulfatase activity, while mucin siali dase activity was unchanged. Metabolically labelled mucin isolated fro m UC patients contained less sulfate and had lower sialic acid O-acety lation compared with normal mucin. Colonic mucin was degraded more eff iciently by faecal extracts from UC patients compared with normal extr acts. The UC mucin was degraded more rapidly than the normal mucin by faecal enzyme extracts from both normal and UC subjects.