The Escherichia coli yjfP gene encodes a carboxylesterase involved in sugar utilization during diauxie. YjfP controls the intracellular concentration of acetyl sugars by redirecting them to the main metabolic circuits
Title: Functional Characterization of a Marine Bacillus Esterase and its Utilization in the Stereo-Selective Production of D-Methyl Lactate Huang J, Zhang Y, Hu Y Ref: Appl Biochem Biotechnol, 180:1467, 2016 : PubMed
Chiral lactic acid and its ester derivatives are crucial building blocks and platforms in the generation of high value-added drugs, fine chemicals and functional materials. Optically pure D-lactic acid and its ester derivatives cannot be directly generated from fermentation and are quite expensive. Herein, we identified, heterologously expressed and functionally characterized one Bacillus esterase BSE01701 from the deep sea of the Indian Ocean. Esterase BSE01701 could enzymatically resolve inexpensive racemic methyl lactate and generate chiral D-methyl lactate. The enantiomeric excess of desired chiral D-methyl lactate and the substrate conversion could reach over 99 % and 60 %, respectively, after process optimization. Notably, the addition of 60 % (v/v) organic co-solvent heptane could greatly improve both the enantiomeric excess of D-methyl lactate and the conversion. BSE01701 was a very promising marine microbial esterase in the generation of chiral chemicals in industry.
Title: The Escherichia coli yjfP Gene Encodes a Carboxylesterase Involved in Sugar Utilization during Diauxie Johns N, Wrench A, Loto F, Valladares R, Lorca G, Gonzalez CF Ref: J Molecular Microbiology Biotechnol, 25:412, 2015 : PubMed
BACKGROUND: Acetylation and efflux of carbohydrates during cellular metabolism is a well-described phenomenon associated with a detoxification process to prevent metabolic congestion. It is still unclear why cells discard important metabolizable energy sources in the form of acetylated compounds. METHODS: We describe the purification and characterization of an approximately 28-kDa intracellular carboxylesterase (YjfP) and the analysis of gene and protein expression by qRT-PCR and Western blot. RESULTS: qRT-PCR and Western blot, respectively, showed that yjfP is upregulated during the diauxic lag in cells growing with a mixture of glucose and lactose. The beta-galactosidase activity in the deltayjfP strain was both delayed and half the magnitude of that of the wild-type strain. YjfP-hyperproducing strains displayed a long lag phase when cultured with glucose and then challenged to grow with lactose or galactose as the sole carbon source. CONCLUSION: Our results suggest that YjfP controls the intracellular concentration of acetyl sugars by redirecting them to the main metabolic circuits. Instead of detoxification, we propose that sugar acetylation is utilized by the cell for protection and to prevent the metabolism of a necessary minimal intracellular sugar pool. Those sugars can eventually be exported as a side effect of these mechanisms.
