Segmented Plasmid Design for Stable Enzyme Expression
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Solution Overview
Problem
Previous attempts to express formate dehydrogenase (FDH) and phenylalanine dehydrogenase (PDH) using a single bi-cistronic plasmid with tandem promoters have resulted in genetic instability, leading to decreased product yield due to processing of the plasmid, which affects the production of synthetic precursor molecules for DPPIV inhibitors like saxagliptin.
Innovation Solution
A stable bi-cistronic plasmid is developed, incorporating specific nucleic acid sequences that encode FDH and PDH, allowing for simultaneous expression of both enzymes under a single promoter, ensuring genetic stability and improved yield of synthetic precursor molecules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single bi-cistronic plasmid with tandem promoters is used to express FDH and PDH, then both enzymes can be expressed simultaneously, but the plasmid becomes genetically unstable and undergoes processing leading to decreased product yield
Solution Approach 1:
The patent divides the bi-cistronic plasmid into two separate monocistronic plasmids, each carrying one gene (FDH or PDH) with its own promoter. This segmentation eliminates the genetic instability caused by the tandem promoter configuration while maintaining the ability to express both enzymes through co-transformation of the host cell with both plasmids.
2Productivity
If tandem promoters are used in a single plasmid to drive expression of both enzymes, then expression of both FDH and PDH is achieved, but the plasmid portion containing the FDH gene is processed (truncated) with each cell generation
Solution Approach 1:
The patent separates the tandem promoter structure into two independent promoter-gene units on separate plasmids. Each plasmid maintains its own promoter and gene without the structural vulnerabilities of the tandem configuration, ensuring both plasmid integrity and continuous expression capability across cell generations.
Solution Approach 2:
The patent introduces a selectable marker gene as an intermediary element on each plasmid to maintain plasmid retention and stability in the host cell population. This mediator ensures that cells maintaining both plasmids are selected for, preventing loss of either plasmid during cultivation and ensuring consistent enzyme production.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The approach provides a genetically stable expression system for FDH and PDH, enhancing the production of synthetic precursors, such as (αS)-α-[[(1,1-dimethylethyoxy)carboxyl]-amino]-3-hydroxytricyclo[3.3.1.13,7]decane-1-acetic acid, crucial for DPPIV inhibitors, with increased yield and stability across multiple generations.
Implementation Method 1
Recombinant expression of the enzymes formate dehydrogenase (FDH) (e.g., from Pichia pastoris (ATCC 20864)) and phenylalanine dehydrogenase (PDH) (e.g., from Thermoactinomyces intermedius (ATCC 33205)) can be used in the biotransformation of 3-hydroxy-α-oxotricyclo-[3.3.1.13,7] decane-1-acetic acid to (αS)-α-amino-3-hydroxytricyclo[3.3.1.13,7] decane-1-acetic acid
Data Source
AI summary
Bi-cistronic plasmids used for the expression of formate dehydrogenase (FDH) and modified phenylalanine dehydrogenase (PDHmod) are provided.