Two family G xylanase genes from Chaetomium gracile and their expression in Aspergillus nidulans

With oligonucleotides based on the amino-terminal and internal amino-acid sequences of a xylanase, two xylanase genes, cgxA and cgxB, were isolated and sequenced from Chaetomium gracile wild and mutant strains. Each gene isolated from both strains was essentially the same as far as nucleotide sequences were compared. The mature CgXA and CgXB xylanases comprise 189 and 211 amino acids, respectively, and share 68.5% homology. The CgXA was found to be the major enzyme in the mutant strain. Comparison of these amino-acid sequences with xylanase sequences from other origins showed that they have a high degree of identity to the family G xylanases. The cgxA and cgxB genes were introduced into Aspergillus nidulans and found to be expressed with their own promoters.