Production, Purification, and Characterization of L-Methioninase Produced by Escherichia coli Isolates: Potential Application in Cancer Treatment

Background: L-methioninase is one of the fascinating enzymes, and it has recently been the subject of intensive research due to its several potential medical uses, L-methionine plays a crucial role in the growth and proliferation of many cancer cells, particularly those seen in specific tumor types. L-methioninase’s ability to lower the body’s levels of L-methionine is the main reason for its strong anti-cancer effects. Objective: To purify and characterize L-methioninase produced by Escherichia coli. Methods: Twenty-one E. coli isolates were screened for L-methioninase production by semi-quantitative and quantitative methods, and then L-methioninase was purified using ammonium sulfate, ion exchange, and gel filtration chromatography. Results: Out of all isolates, 16/21 (76.19%) were L-methioninase producers by semi-quantitative, while by quantitative screening, only six isolates out of these 21 isolates revealed specific activity ranged from 0.89 to 1.15 U/mg, and the maximum specific activity was for E. coli U8. The L-methioninase was purified using ammonium sulfate, ion exchange, and gel filtration chromatography. The best saturation ratio for L-methioninase precipitation was at 70% ammonium sulfate, considered a partial purification where L-methioninase specific activity was 2.52 U/mg. while L-methioninase-specific activity reached 4.11 U/mg when ion exchange chromatography was used with 3.2-fold purification and a yield of 46.2%. Finally, a pure L-methioninase-specific activity of 6.48 U/mg was gained using gel filtration with 5.1-fold purification and a yield of 42.9%. Determining molecular weight characterized the purified L-methioninase; the result showed that the purified L-methioninase had a molecular 50 kDa. Conclusions: L-methioninase was purified from E. coli by many steps, including ammonium sulfate precipitation, DEAE-cellulose, and Sephedex G-150, in addition, SDS-PAGE electrophoresis supports the success of the purification process.