Upregulation of promoter activity of the Aspergillus oryzae xylanase gene by site-directed mutagenesis.

In Aspergillus oryzae, inductive expression of the xynF1 gene is mediated by a transcriptional activator, AoXlnR. Promoter activity of the xynF1 gene, monitored by beta-galactosidase activity, was successfully upregulated by mutating two non-canonical AoXlnR binding sequences to what is thought to be the strongest sequence. Transformants carrying three canonical binding sequences in the promoter region produced enzyme 2.8 times more active (33,000 units mg(-1) protein) than that of transformants carrying the authentic promoter (12,000 units mg(-1) protein).