Mutant CadA Enzyme Alkaline pH Stability
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Solution Overview
Problem
Acid decarboxylases, such as CadA, have limited functional stability and activity outside a narrow pH range, leading to decreased performance and increased salt production in biochemical processes, which is costly and environmentally impactful.
Innovation Solution
A mutant CadA variant with specific amino acid substitutions at positions 457, 458, and 460, allowing the enzyme to maintain activity and stability across a wider pH range without the need for additional pH-maintaining chemicals, thereby reducing salt production and process costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wild-type acid decarboxylase is used, then the enzyme functions optimally within a narrow pH range, but the activity decreases significantly outside that pH range
Solution Approach 1:
The patent applies parameter changes by modifying the amino acid sequence of the acid decarboxylase enzyme through site-directed mutagenesis. Specific residues (Asp457, His458, Asp460) are mutated to alter the enzyme's pH sensitivity parameters, shifting its optimal activity range and broadening its functional stability to operate effectively at both acidic and alkaline pH conditions.
2Reliability
If pH-maintaining chemicals are added to maintain optimal pH, then enzyme activity is maintained, but salt production increases and process costs increase
Solution Approach 1:
The patent implements self-service by engineering the enzyme to autonomously maintain its own optimal activity conditions across varying pH environments. The mutant acid decarboxylase inherently resists pH-induced inactivation and aggregation without requiring external pH-maintaining chemicals, thereby eliminating salt waste and reducing operational costs while maintaining high enzyme activity.
3Productivity
If wild-type acid decarboxylase is used at alkaline pH, then the reaction can proceed, but the enzyme aggregates into higher molecular weight complexes and function decreases
Solution Approach 1:
The patent applies parameter changes by mutating specific amino acid residues (Asp457, His458, Asp460) that are involved in pH-dependent protein-protein interactions. These mutations alter the electrostatic parameters and charge distribution on the enzyme surface, preventing pH-induced aggregation and maintaining stable monomeric or functional oligomeric structure across a broad pH range, thereby sustaining high reaction rates at alkaline pH.
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 mutant CadA variant enhances lysine conversion to cadaverine at alkaline pH, reducing salt waste and operational costs while maintaining high reaction rates, thus improving process efficiency and environmental sustainability.
Implementation Method 1
The class of proteins known as acid decarboxylases is a group of enzymes that catalyze the decarboxylase reaction of basic amino acids (e.g., lysine, arginine, ornithine) in order to generate polyamines
Implementation Method 2
one of the dominant reactions in a protein-water solution is the exchange of protons by certain amino acids with the environment of the protein
Implementation Method 3
The pKa is a measure of the difference in free energy between neutral and charged states, and indicates the propensity of an amino acid to donate or accept a proton
Implementation Method 4
Charged groups can interact with other charged groups when the two groups are brought into proximity of one another. Like charges repel each other and opposite charges attract each other
Data Source
AI summary
The invention provides CadA polypeptides with mutations that increase activity in alkaline pH compared to the wild-type lysine decarboxylase. The invention also provides methods of generating such mutant polypeptides, microorganisms genetically modified to overexpress the mutant polypeptides, and methods of generating such microorganisms.