EXPRESSION OF TRICHODERMA-REESEI AND TRICHODERMA-VIRIDE XYLANASES IN ESCHERICHIA-COLI

Synthetic genes encoding the 190 amino acid Trichoderma reesei xylanas e II (TrX) and the closely related Trichoderma viride xylanases have b een synthesized in a two-step procedure. Initially, a partial gene enc oding amino acids 92-190 was constructed in fusion with the N-terminal half of the Bacillus circulans xylanase (BcX). The remaining BcX gene sequence was replaced during the assembly of the coding sequence for amino acids 1-91. Expression of the synthetic genes in Escherichia col i yielded recombinant xylanases with specific activity generally ident ical with the natural TrX. However, the recombinant TrX showed thermos tability and temperature optimum lower than those of the natural TrX, thus indicating that the posttranslational modifications of the latter in its fungal host are essential to its greater stability. A mutation N19K further decreased the thermostability of the recombinant TrX.