ISOLATION AND CHARACTERIZATION OF A 1,4-BETA-ENDOXYLANASE GENE OF A-AWAMORI

An enzyme with a particular 1,4-beta-xylanase activity was identified and purified from wheat-bran culture medium of an Aspergillus awamori strain. With oligonucleotides based on the N-terminal amino-acid seque nce of the enzyme, the exlA gene of A. awamori, encoding 1,4-beta-xyla nase A, has been cloned. Based on the deduced amino-acid sequence, 1,4 -beta-xylanase A is produced as a 211 amino-acid-residue-long precurso r, which is converted post-translationally into a 184-aa-residue-long mature protein. Transformation of the original A. awamori strain with multiple copies of the exlA gene resulted in a 40-fold overproduction of 1,4-beta-xylanase A. The overproduced enzyme has the same biochemic al and enzymological properties as the wild-type enzyme.