Cloning and characterization of the gene for the thermostable xylanase XynA from Thermomyces lanuginosus

A thermostable xylanase from the filamentous fungus Thermomyces lanuginosus (DSM 5826) was purified. This enzyme has an apparent molecular weight of 24-26 kDa as determined by SDS polyacrylamide gel electrophoresis. cDNA and genomic DNA fragments coding for this enzyme were cloned and sequenced. The cDNA contains an open reading frame encoding a polypeptide of 225 amino acids and was functionally expressed in E. coli as a LacZ fusion protein. Comparison of the cDNA sequence with the genomic DNA sequence showed that the xylanase was encoded by two exons interrupted by an intron of 106 bp. Comparison of the deduced amino acid sequence to other published xylanases revealed high homology to xylanases of the family G glycanases.