Two xylanases from Gaeumannomyces graminis with identical N-terminal amino acid sequence

Abstract

Gaeumannomyces graminis var. avenae produces extracellular xylanase activity when grown in minimal medium containing xylan as sole carbon source. A 26·5 kDa and a 28 kDa xylanase were isolated from culture filtrates of the fungus grown on xylan. Both xylanases had a pI of 10·5 and behaved very similarly during hydrophobic interaction, cation exchange, and size exclusion chromatography. Enzyme activity of the combined xylanases was maximal at 50 °C and between pH 5·0 and 5·5. The N-terminal amino acid sequences of the two xylanases were identical and showed strong homology with xylanase from Schizophyllum commune and three other microbial xylanases. Xylanase activity with similar properties to the enzymes purified from culture fluids was detected in oat and wheat roots infected with G. graminis var. avenae but was not detected in healthy roots.