The nitrate reductase gene from a shoyu koji mold, Aspergillus oryzae KBN616.

A niaD gene encoding nitrate reductase was isolated from Aspergillus oryzae KBN616 and sequenced. The structural gene comprises 2973 bp and 868 amino acids, which showed a high degree of similarity to nitrate reductases from other filamentous fungi. The coding sequence is interrupted by six introns varying in size from 48 to 98 bp. The intron positions are all conserved among the niaD genes from A. oryzae, Aspergillus nidulans, and Aspergillus niger. A homologous transformation system was developed for an industrial shoyu koji mold, A. oryzae KBN616, based on the nitrate reductase (niaD) of the nitrate assimilation pathway.