Talaromyces emersonii enzyme systems

摘要

Talaromyces emersonii secretes between 14-20 distinct endoxylanase components when grown on the appropriate carbon source. Thirteen of these endoxylanases have been purified to homogeneity and characterized with respect to catalytic properties. The molecular weights of the purified endoxylanases vary between 30-130 kDa. Xylanase and glucanase expression is not equivalent between 10 Talaromyces emersonii strains grown under identical conditions on the same nutrient medium and carbon inducers. A new low molecular weight xylanase has been identified, Xyn XII (17.5 kDa) from the xylan-degrading system of the T. emersonii IMI393751 strain. The temperature optimum for Xyn XII-catalyzed degradation of the arabinoxylan OSX was determined to be 75 °C, and the optimum pH for activity was pH 4.0 - 4.5. Xyn XII was remarkably acid stable and retained over 91 % of its original activity at pH 3.0.
Xyn XII is most active on a mixed-linkage, unsubstituted D-xylan. It displayed substantial activity against mixed-linkage D-glucans, and it displayed activity against aryl-²-xylosides. In vivo, Xyn XII may play a very important role for T. emersonii IMI393751 in providing access to plant cell wall hemicellulose.