High expression and activity of an L-methionine γ-lyase gene in Escherichia coli

Abstract:

[Background] In order to develop new microbial resources in the ocean, our laboratory constructed a deep sea metagenomic library by adopting the culture-independent metagenomic technology, and carried out follow-up studies on the important genes. [Objective] To identify and highly express the methionine γ-lyase gene in Escherichia coli from the DNA library of deep-sea sediments. [Methods] The gene mgl was overexpressed by pET-28a(+) system in E. coli BL21(DE3), which was induced by isopropyl β-D-1-thiogalactopyranoside, and the expression conditions were optimized to obtain the high expression of methionine-lyase (rMGL). The recombinant protein was purified by affinity chromatography and the enzyme activity was studied. [Results] The product rMGL was consistent with the predicted 46 kD, with high L-methionine lyase activity. rMGL could use L-methionine and DL-homocysteine as substrate, but had little activity on L-cysteine and L-cystine. Its relative activity on DL-homocysteine was 1.4 times of that on L-methionine. [conclusion] mgl gene from the deep sea metagenomic library can efficiently express rMGL using pET-28a(+)/BL21(DE3).