Polymorphism
See Also
Abstracts
Degradation of blood group antigens in human colon ecosystems. II. A gene interaction in man that affects the fecal population density of certain enteric bacteria
J Clin Invest. 1976 Jan;57(1):74-82. Hoskins LC, Boulding ET.
- The autosomal dominant ABH secretor gene together with the ABO blood type gene control the presence and specificity of A, B, and H blood group antigens in human gut mucin glycoproteins. Certain obligate anaerobes in feces produce extracellular antigen-specific glycoside structures. We estimated the populations of these bacteria in feces of 22 healthy subjects by determining the greatest dilution of feces that yielded A, B, or H blood group-degrading enzyme activity after 24 h incubation in anaerobic cultures. Comparatively small populations of fecal bacteria produce blood group-degrading enzymes; their estimated populations were 10(8) per g or less in 21 subjects. Fecal populations of B-degrading bacteria were stable over time, and their population density averaged 50,000-fold greater in blood group B secretros than in other subjects. We present evidence that the greater fecal populations of B-degrading bacteria in B secretors is due in part to a competitive nutritional advantage gained by their ability to enzymatically cleave the B antigenic determinant alpha-D-galactose from gut mucins of B secretors. Fecal populations of bacteria producing A and H antigen-degrading enzyme activities were comparable in all subjects to the fecal population of B-degrading bacteria in B secretors. The large populations of fecal anaerobes may be an additional source of A antigen substrate for A-degrading bacteria; thus, antigens cross-reacting with A antigen were detected on cell walls of anaerobic bacteria from 3 of 10 cultures inoculated with 10(-10) g feces. Bacteria producing B-degrading activity likely represent a separate population from those producing A- or H-degrading activity since their fecal populations differed numerically in 14 subjects. These findings suggest that adaptation of blood group-degrading enzymes to mucin structures in human colon ecosystems is chiefly by mutation-selection of comparatively small populations of constitutive enzyme-producing strains rather than by substrate induced enzyme synthesis in many strains.
- Full Article
Degradation of blood group antigens in human colon ecosystems. I. In vitro production of ABH blood group-degrading enzymes by enteric bacteria
J Clin Invest. 1976 Jan;57(1):63-73. Hoskins LC, Boulding ET.
- Human feces contain enzymes produced by enteric bacteria that degrade the A, B, and H blood group antigens of gut mucin glycoproteins. We have studied their production in fecal cultures to determine if such cultures can be a source for enzyme purification and to explore how blood group antigen-degrading enzymes are adapted in individual human colon ecosystems. They were present in fecal cultures from each of 27 healthy subjects, including ABH nonsecretors. Heat-sensitive obligate anaerobes are their major source. From 39 to 85% of the total enzyme activity produced by growing cultures was extracellular. Commercial hog gastric mucin and salivary glycoproteins, including Lea saliva which lacks A, B, and H antigens, enhance production of A-, B-, and H-degrading activity in anaerobic fecal cultures irrespective of the glycoprotein's blood group specificity. There is evidence that the host's ABO blood type and secretor status affects the specificity of blood group-degrading enzymes produced by his fecal bacteria in vitro. Thus, fecal inocula from B secretors incubated with hog gastric mucin (A and H specificity) or with Lea saliva produced greater levels of B-degrading than A- or H-degrading activity, and inocula from A secretors in similar media produced greater levels of A-degrading than B- or H-degrading activity. Blood group-degrading enzymes produced in fecal cultures are glycosidases and not proteases. The B-degrading enzyme cleaves the B antigenic determinant alpha-D-galactose from the oligosaccharide side chains of mucin glycoproteins with B specificity. Anaerobic fecal cultures containing blood group substances are a feasible source for purifying blood group antigen-degrading enzymes. Prior adaptation to blood group antigens in the gut mucins of type A and type B secretors affects the specificity of the enzymes produced in vitro.
Discussion
Links
- Degradation of human intestinal glycosphingolipids by extracellular glycosidases from mucin-degrading bacteria of the human fecal flora G Larson, P Falk, and LC Hoskins J. Biol. Chem., Aug 1988; 263: 10790 - 10798. PDF File
