title: Degradation of hemicellulose and pectin by horse caecum contents.
abstract: 1. Polysaccharide depolymerases and glycoside hydrolases involved in the breakdown of plant structural polysaccharides (hemicellulose and pectins) were monitored in three fractions of the liquid phase of horse caecum digesta: acellular fluid (AF), bacteria (B) and protozoa plus bacteria (PB). 2. Both bacteria and protozoa were found to be involved in the decomposition of pectic substances, with two enzymic activities: depolymerase (polygalacturonase, EC 3.2.1.15; and pectin lyase, EC 4.2.2.10) and esterase (pectinesterase, EC 3.1.1.11). The activity of the PB fraction was higher than that of B. 3. With hemicellulosic substrates, all three fractions showed a significant xylan endo-1,3-beta-xylosidase (EC 3.2.1.32) activity. Mannan was hardly broken down. 4. Galactomannan and arabinogalactan were broken down more extensively by the PB fraction than by the B fraction. Glycosidase activities (xylan 1,4-beta-xylosidase, EC 3.2.1.37 and alpha-L-arabinofuranosidase, EC 3.2.1.55) were also observed.
authors.affiliation: L.A. CNRS n degrees 138, Groupe de Zoologie et Protistologie, Aubiere, France.
authors.forename: A
authors.initials: A
authors.lastname: Bonhomme-Florentin
mesh_terms: D000818:Animals; D002265:Carboxylic Ester Hydrolases / Q000378:metabolism; D002432:Cecum / Q000378:metabolism*; D004063:Digestion; D006026:Glycoside Hydrolases / Q000378:metabolism; D006736:Horses / Q000378:metabolism*; D010368:Pectins / Q000378:metabolism*; D011096:Polygalacturonase / Q000378:metabolism; D011133:Polysaccharide-Lyases / Q000378:metabolism; D011134:Polysaccharides / Q000378:metabolism*
chemical_list: D011134:Polysaccharides; C007916:hemicellulose; D010368:Pectins; D002265:Carboxylic Ester Hydrolases; C022323:pectinesterase; D006026:Glycoside Hydrolases; D011096:Polygalacturonase; D011133:Polysaccharide-Lyases; C027349:pectin lyase