Local metabolic response of Escherichia coli to the module genetic perturbations in L-methionine biosynthetic pathway

摘要

L-Methionine biosynthesis is through multilevel regulated and multibranched biosynthetic pathway (MRMBP).Because of the complex regulatory mechanism and the imbalanced metabolic flux between branched pathways, microbial production of L-methionine has not been commercialized.In this study, local metabolic response in MRMBP of L-methionine was investigated and various crucial genes in branched pathways were determined.In L-serine pathway, the crucial gene was serABC.In O-succinyl homoserine (OSH) pathway, which was the C4 backbone of L-methionine, metB and metL controlled the metabolic flux jointly.In L-cysteine pathway, the crucial gene cysE~(fbr) could disturb the flux distribution of local network in L-methionine biosynthesis.However, no crucial gene for L-methionine production in 5-methyl tetrahydrofolate (CH3-THF) pathway was found.The relation between these pathways was also researched.L-Serine pathway, as the upstream pathway of L-cysteine and CH3-THF, played a crucial role in L-methionine biosynthesis.L-Cysteine pathway showed the strongest controlling force of the metabolic flux, and OSH pathway was second to L-cysteine pathway.In contrast, CH3-THF pathway was the weakest, which was probably the mainly limited steps at present and had great potential in further research.In addition, constructed W3110 IJAHFEBC/pA HAmL was able to produce 2.62 g/L L-methionine in flask.This study is instructive for L-methionine biosynthesis and provides a new research method of biosynthesizing other metabolic products in MRMBPs.