Abstract
2-C-Methyl-D-erythritol-4-phosphate (MEP) pathway has been extensively employed for terpenoids biosynthesis in Escherichia coli. In this study, to obtain key-enzymes of MEP pathway for squalene production, overexpression of different combination of MEP pathway genes were compared. Squalene production in strain YSS12 with overexpressed dxs, idi and ispA of MEP pathway from E. coli was improved by 71-fold when compared with strain YSS3 which only contained double copy SQS. Analysis of transcriptional levels of MEP pathway genes in engineering strains showed that different squalene production can be attributed to changed transcriptional levels of co-overexpressed genes dxs, idi, ispG and ispA in engineering strains. Furthermore, different E. coli expression hosts were compared for squalene production, among which BL21(DE3) was the best squalene producer. These results illustrate that dxs, idi and ispA of the MEP pathway from E. coli were key-enzymes for squalene production in E. coli. These key-enzymes of MEP pathway could also be applied to other terpenoids production in E. coli. Key words: Squalene, key-enzyme, 2-C-methyl-D-erythritol-4-phosphate (MEP) pathway, Escherichia coli.
Highlights
Squalene is a triterpene with a unique 30-carbon, polyunsaturated hydrocarbon and has a variety of pharmacological activities such as reduction of serum cholesterol levels (Hien et al, 2017), anticancer (Kotelevets et al, 2017), modulating fatty acid metabolism (Kumar et al, 2016), and is extensively used in the functional food, cosmetic and pharmaceutical industries.Naturally, squalene is derived from two universal precursors, isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP), which are synthesized via the 2-C-methyl-D-erythritol-4-phosphate (MEP), or mevalonate (MVA) pathway (Banerjee and Sharkey, 2014)
E. coli can synthesize farnesyl diphosphate (FPP) which is a precursor of squalene by a native MEP pathway, it is unable to produce the squalene because of the absence of squalene synthase (SQS)
These results suggested that SQS from Y. lipolytica can be used for the biosynthesis of squalene in E. coli
Summary
Squalene is derived from two universal precursors, isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP), which are synthesized via the 2-C-methyl-D-erythritol-4-phosphate (MEP), or mevalonate (MVA) pathway (Banerjee and Sharkey, 2014). IPP and DMAPP are condensed to form geranyl diphosphate (GPP) by FPP synthase, and subsequently condensed with another IPP to produce farnesyl diphosphate (FPP). Squalene is biosynthesized by a NADPH-mediated reaction catalyzed by squalene synthase (SQS) using FPP as the substrate (Ghimire et al, 2016) (Figure 1).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
