Attenuated Citrate Synthase for Higher L-Amino Acid Productivity
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Solution Overview
Problem
Existing Corynebacterium strains with deleted gltA gene for citrate synthase exhibit inhibited growth and reduced sugar consumption rates, leading to low L-amino acid production per unit time.
Innovation Solution
A modified polypeptide with attenuated citrate synthase activity is introduced by substituting the 312th amino acid in the citrate synthase sequence, increasing L-amino acid production without affecting sugar consumption rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the gltA gene encoding citrate synthase is deleted to increase L-amino acid production, then L-amino acid yield is improved, but growth rate and sugar consumption rate are significantly reduced
Solution Approach 1:
The invention applies parameter changes by substituting specific amino acids at positions 312, 316, or 321 in the citrate synthase polypeptide sequence. These amino acid substitutions modify the enzyme's catalytic activity parameters, creating an attenuated citrate synthase that allows sufficient carbon flow to the TCA cycle for growth while redirecting enough carbon to oxaloacetate for L-amino acid biosynthesis, thereby resolving the contradiction between yield and productivity
2Quantity of substance
If citrate synthase activity is completely inhibited to redirect carbon flow, then L-amino acid biosynthesis is improved, but cell growth is inhibited
Solution Approach 1:
The invention applies partial action by partially inhibiting citrate synthase activity rather than completely blocking it. The amino acid substitutions reduce enzyme activity to a level that is sufficient to redirect carbon flux toward oxaloacetate and L-amino acid biosynthesis, while maintaining enough activity to support essential TCA cycle function and cell growth, thus resolving the contradiction between biosynthesis improvement and growth maintenance
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 polypeptide balances carbon flow, enhancing L-amino acid yield while maintaining sugar consumption rates, thus improving L-amino acid production efficiency.
Implementation Method 1
Citrate synthase (CS) is an enzyme that produces citrate by catalyzing the condensation of acetyl-CoA and oxaloacetate
Data Source
AI summary
The present disclosure relates to a modified polypeptide with attenuated activity of citrate synthase, a microorganism producing leucine comprising the modified polypeptide, and a method for producing an L-amino acid using the microorganism.