Ketol-acid Reductoisomerase Enzymes for Isobutanol Biosynthesis
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Solution Overview
Problem
Current methods for producing isobutanol rely on petrochemical-derived starting materials and lack environmental advantages, such as minimized greenhouse gas emissions, and there is a need for alternative polypeptides with ketol-acid reductoisomerase activity suitable for isobutanol biosynthetic pathways.
Innovation Solution
Development of polypeptides with specific substitutions in regions like the inter-molecular dimer interface, inter-domain interface, and C-terminal tail region, which exhibit ketol-acid reductoisomerase activity, enhancing isobutanol production by improving reaction rates and reducing substrate competition and inhibition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If chemical synthesis methods (oxo synthesis, catalytic hydrogenation, Guerbet condensation) are used to produce isobutanol, then production efficiency is achieved, but environmental harm increases due to petrochemical-derived starting materials and greenhouse gas emissions
Solution Approach 1:
The invention changes the fundamental parameter of starting material origin from petrochemical to plant-derived renewable resources. This parameter change enables biochemical conversion pathways that avoid the harmful emissions associated with traditional chemical synthesis methods while maintaining production efficiency through enzymatic catalysis
Solution Approach 2:
The invention replaces mechanical/chemical synthesis systems with biological enzymatic systems. Specifically, ketol-acid reductoisomerase enzymes catalyze the conversion of plant-derived substrates to isobutanol, substituting the mechanical chemical synthesis processes with biologically-based enzymatic reactions that are environmentally benign
2Productivity
If wild-type KARI enzymes are used in isobutanol biosynthetic pathways, then baseline production is achieved, but productivity is limited due to substrate competition and inhibition
Solution Approach 1:
The invention applies local quality changes by introducing specific amino acid substitutions at particular positions within the KARI enzyme structure. These localized changes in the enzyme's active site or regulatory regions enhance its catalytic efficiency and reduce susceptibility to substrate competition and inhibition, thereby improving overall productivity
Solution Approach 2:
The invention changes the biochemical parameters of the KARI enzyme through site-directed mutagenesis. By modifying amino acid sequences, the enzyme's kinetic parameters (such as Km and Vmax) are optimized to reduce substrate competition effects and inhibition, enabling higher isobutanol yields from plant-derived substrates
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 modified polypeptides increase isobutanol production yield by up to 100% compared to wild-type enzymes, utilizing plant-derived substrates and reducing environmental impact.
Implementation Method 1
Ketol-acid reductoisomerase (KARI) enzymes are involved in the biological production of valine and isoleucine. KARI enzymes have also been shown to be useful for pathways for the production of isobutanol using engineered microorganisms
Implementation Method 2
A KARI enzyme that can utilize reduced nicotinamide adenine dinucleotide (NADH) can capitalize on the NADH produced by the existing glycolytic pathway and other metabolic pathways in commonly used microbial cells
Data Source
AI summary
Provided herein are polypeptides having ketol-acid reductoisomerase activity as well as microbial host cells comprising such polypeptides. Polypeptides provided herein may be used in biosynthetic pathways, including, but not limited to, isobutanol biosynthetic pathways.