| Characterization of Xylan Hydrolysis by Xyn10B and Axe1B from Acidothermus cellulolyticus 11B Xylan, a major component of plant cell walls, is the second most abundant polysaccharide in nature and thus represents a major source of renewable carbon. Microorganisms employ several enzymes to deconstruct the polymer in order to utilize the monomers for carbon and energy. This study describes two such enzymes, a xylanase designated Xyn10B and an acetyl esterase designated Axe1B produced by the actinomycete Acidothermus cellulolyticus strain 11B, and explores their ability to deconstruct birchwood xylan. The genes that encode each protein were found to be cotranscribed during growth on xylan. A maximum activity of 0.36 mumoles min-1 mg-1 on 4-methylumbelliferyl-O-acetate at 75° C and pH 5 was observed for partially purified recombinant Axe1B and a maximum activity of 28.6 mumoles mg-1 min-1 on birchwood xylan at 80° and pH 5 was observed for partially purified recombinant Xyn10B. In addition, Axe1B was found to enhance the extent of hydrolysis of birchwood xylan and chemically acetylated birchwood xylan by Xyn10B up to 32% and 77% respectively. |
