Engineered E. coli NADP-GAPDH for NADPH Yield
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Solution Overview
Problem
Natural organisms are not optimized for producing NADPH-dependent bioproducts, leading to limited yield and productivity due to insufficient intracellular NADPH levels, which is a challenge in bioproduction processes such as PHB synthesis and the use of NADPH-dependent enzymes for chemical processes.
Innovation Solution
Engineered E. coli strains with reduced NADH-dependent glyceraldehyde-3-phosphate dehydrogenase (NAD-GAPDH) activity and increased NADP-dependent glyceraldehyde-3-phosphate dehydrogenase (NADP-GAPDH) activity to enhance intracellular NADPH availability, achieved through inhibition, inactivation, or overexpression of NADP-GAPDH enzymes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If natural organisms are used for bioproduction, then the process is simple and natural, but the intracellular NADPH levels are insufficient leading to limited yield and productivity
Solution Approach 1:
The patent changes the cofactor specificity parameter of GAPDH enzyme from NAD+-dependent to NADP+-dependent. This fundamental parameter change redirects the glycolytic pathway to produce NADPH instead of NADH, directly increasing intracellular NADPH levels and enabling higher productivity of NADPH-dependent bioproducts without complicating the overall metabolic pathway structure
Solution Approach 2:
The patent introduces a heterologous NADP+-dependent GAPDH gene from another organism into E. coli. This copied enzyme replaces or supplements the native NAD+-dependent GAPDH, providing the desired NADPH-producing function while maintaining compatibility with the host cellular machinery and metabolic network
2Quantity of substance
If NADPH levels are increased through conventional methods, then NADPH availability improves, but cell damage or reduced product production ability occurs
Solution Approach 1:
The engineered E. coli strain produces NADPH endogenously through the modified glycolytic pathway using NADP+-dependent GAPDH. This self-service mechanism generates NADPH directly within the metabolic pathway where it is needed, avoiding the need for external supplementation or induction of stress responses that could damage cells or reduce product production capability
Solution Approach 2:
The NADP+-dependent GAPDH operates continuously during glycolysis to generate NADPH as a byproduct of glucose metabolism. This continuous production integrates NADPH generation into the primary energy-generating pathway, ensuring steady NADPH supply without requiring separate induction steps or creating metabolic imbalances that could harm cell viability
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 engineered strains produce at least 30% more NADPH, leading to increased production of NADPH-dependent compounds like PHBs, lycopene, lactones, and pharmaceutical intermediates, with preferred embodiments achieving 40% or 50% more NADPH, thereby enhancing bioproduction efficiency.
Implementation Method 1
NADP-dependent glyceraldehyde-3-phosphate dehydrogenase (NADP-GAPDH)
Implementation Method 2
The cofactor pair NADPH/NADP+ plays a central role as donors and/or acceptors of reducing equivalents during anabolic metabolism
Data Source
AI summary
A method of increasing cellular NADPH levels by expressing one or more genes that encode an enzyme that causes the production of NADPH. The system is combined with other enzymes that require NADPH, thus improving the overall yield of the desired product.