Mucin degradation in human colon ecosystems. Degradation of hog gastric mucin by fecal extracts and fecal cultures

The enteric flora of rats plays a major role in the degradation of their gut mucin glycoproteins, but the role of human enteric flora in degrading gut mucin glycoprotein has not been as well defined. We have studied the degradation of hog gastric mucin, which is structurally similar to human gastric mucin, in anaerobic human fecal cultures and by partially purified enzyme fractions from human fecal extracts and anaerobic culture supernates. Extensive degradation of the mucin carbohydrate moieties occurred in all systems, but the degradation of mucin protein was less. During a 48-h incubation, the average percent degradation of mucin carbohydrates and mucin protein were respectively 96% and 57% in eight fecal cultures, 66% and 15% by four fecal culture supernates, and 78% and 43% by three fecal extracts. Degradation of mucin protein was greater during bacterial growth in fecal cultures than during incubation with fecal culture supernates, suggesting that bacterial protease activity was predominantly cell bound. We conclude that, as in the rat, the human enteric microflora degrades mucin carbohydrate moieties extensively and the mucin protein to a lesser extent.