Heterologous expression and enzymological characterization of L-glutamate oxidase from the marine actinomycete <i>Streptomyces lydicamycinicus</i> NBRC 110027

We successfully constructed a heterologous expression system for L-glutamate oxidase from the marine actinomycete Streptomyces lydicamycinicus NBRC 110027 (Sl-LGOX) in Escherichia coli BL21(DE3) as a host. This is the first example of L-glutamate oxidase from a marine microorganism. A chemically synthesized gene optimized for codon usage in E. coli was used as the inserted fragment, which was effective for enzyme expression. We expressed Sl-LGOX in the soluble fraction of E. coli BL21(DE3)/pET21b-Sl-lgox. We also succeeded in purifying the recombinant Sl-LGOX (rSl-LGOX) to homogeneity from the cell-free extract of this clone via an Ni-NTA column. rSl-LGOX showed high specificity for L-Glu and was active and stable over a wide range of temperatures and pH values. In particular, it showed high specific activity and stability at an acidic pH. A variety of applications can take advantage of the unique enzymatic properties of rSl-LGOX.