Glutaminase is an enzyme that catalyzes the hydrolysis of L-glutamine to L-glutamatic acid. Glutaminase plays an important role to enhance umami taste in fermented food production. Using EST information of Aspergillus oryzae, we cloned a novel glutaminase-encoding gene, AsgahA, from Aspergillus sojae which was similar to a salt-tolerant, thermostable glutaminase of Cryptococcus nodaensis. The structural gene was 1929 bp long with no intron. This glutaminase protein, AsGahA, had an amidase motif, and showed 36% homology to that of C. nodaensis. Introduction of multiple copies of AsgahA intoA. oryzae RIB40 resulted in over expression of glutaminase activity. AsGahA was located at cell surface. AsGahA was subsequently purified from over expressing strain, and characterized. The molecular mass was estimated as 67 kDa by SDS-PAGE while it was estimated as 135kDa by gel filtration chromatography, which indicated that native form of AsGahA was a dimer. Its pH optimum was 9.5 and its temperature optimum was 50 degrees C. Analysis of substrate specificity revealed that AsGahA catalyzed not only L-glutamine but also L-asparagine, and was revealed as a glutaminase-asparaginase.
Fungal Genet. Newsl. 50 (Supl):abstract
Full conference title:
22nd Fungal Genetics Conference
- Fungal Genetics Conference 22nd (2001)