Mucin degradation in the human colon: production of sialidase, sialate O-acetylesterase, N-acetylneuraminate lyase, arylesterase, and glycosulfatase activities by strains of fecal bacteria.
Oligosaccharide side chains of human colonic mucins contain O-acetylated sialic acids and glycosulfate esters. Although these substituents are considered to protect the chains against degradation by bacterial glycosidases, sialate O-acetylesterase, N-acetylneuraminate lyase, and glycosulfatase activities have been found in fecal extracts. To better define the source of these activities, we measured extracellular and cell-bound sialidase, sialate O-acetylesterase, N-acetylneuraminate lyase, arylesterase, and glycosulfatase activities produced by 23 isolates of human fecal bacteria grown anaerobically in a hog gastric mucin culture medium; these represented dominant populations of fecal anaerobes, facultative anaerobes, and the subset of mucin oligosaccharide-degrading bacteria. Every strain produced sialidase and high levels of arylesterase, and all but five facultative anaerobes produced sialate O-acetylesterase. Sialic acids containing 2 mol or more of O-acetyl ester per mol of sialic acid were cleaved from mucin glycoproteins more slowly by sialidases of mucin oligosaccharide-degrading stains than were sialic acids containing 1 or 0 mol, and only N-acetyl- and mono-O-acetylated sialic acids were recovered from enzyme digests of a mucin containing di-O-acetylated sialic acids. No detectable N-acetylneuraminate lyase activity was produced by any strain, but low activity was induced by increasing the glycoprotein-bound sialic acid concentration in the culture medium of six Escherichia coli strains. Using lactitol-6-sulfate as a substrate, we found weak glycosulfatase activity in the partially purified, concentrated enzyme mixture in the culture supernatants of four mucin oligosaccharide-degrading strains but in none of the unconcentrated culture fractions. We conclude that the presence of two or more O-acetyl groups on sialic acids inhibits enteric bacterial sialidases but that production of sialate O-acetylesterases by several populations of enteric bacteria lessens the likelihood that mucin oligosaccharide chains terminating in O-acetylated sialic acids are protected from degradation. Sialate O-acetylesterases have a role in bacterial degradation of mucin glycoproteins in the human colon.
Corfield
A P
AP
University Department of Medicine Laboratories, Bristol Royal Infirmary, United Kingdom.
Wagner
S A
SA
Clamp
J R
JR
Kriaris
M S
MS
Hoskins
L C
LC
D000107:Acetylation; D000115:Acetylesterase; D001419:Bacteria / Q000201:enzymology*; D002265:Carboxylic Ester Hydrolases / Q000096:biosynthesis*; D003106:Colon / Q000378:metabolism*; D004795:Enzyme Stability; D005243:Feces / Q000382:microbiology*; D006801:Humans; D009077:Mucins / Q000378:metabolism*; D019158:N-Acetylneuraminic Acid; D009439:Neuraminidase / Q000096:biosynthesis*; D007652:Oxo-Acid-Lyases / Q000096:biosynthesis*; D012794:Sialic Acids / Q000378:metabolism; D013429:Sulfatases / Q000096:biosynthesis*
D009077:Mucins; D012794:Sialic Acids; D002265:Carboxylic Ester Hydrolases; C019734:arylesterase; D000115:Acetylesterase; C046298:sialate O-acetylesterase; D013429:Sulfatases; C022758:glycosulphatase; D009439:Neuraminidase; D007652:Oxo-Acid-Lyases; C018728:N-acetylneuraminate lyase; D019158:N-Acetylneuraminic Acid