Abstract: For a better understanding of the distribution and basic characteristics of the proteins with glutaminase activity from the microbial flora in the fermented mash of soy sauce, bioinformatics was used to conduct their classification, screening, signal peptides analysis, phylogenetic tree analysis, physicochemical properties prediction and homology modeling of 3-dimensional (3-D) structure. It was found that the proteins with glutaminase activity were divided into 3 categories, participating in glutamine catabolism, biosynthesis and transamination of glutamine, respectively. None of the proteins with glutaminase activity contained signal peptide sequence except 4 glutaminases. Two distinct evolutionary directions were found between bacterial and fungal glutaminase groups by phylogenetic tree analysis. Secretory glutaminases showed slight hydrophilicity with pIs of 4.81?5.99. The structural homology between glutaminases from Enterobacter lignolyticus, Citrobacter freundii and those from Escherichia coli and Bacillus subtilis was shown by 3-D homology modeling.

Key words: glutaminase, soy sauce, microbial flora, sequence analysis