Modified TdT Enzymes Template-Independent Oligonucleotide Synthesis
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Solution Overview
Problem
Current methods for de novo nucleic acid synthesis, such as phosphoramidite techniques, are limited by high breakage rates and side reactions for long sequences, produce toxic waste, and are costly, necessitating more efficient and cost-effective approaches.
Innovation Solution
Modified terminal deoxynucleotidyl transferase (TdT) enzymes that can incorporate 3′-O-blocked nucleotide analogs for template-independent synthesis, allowing for stepwise assembly of polynucleotides with reduced chemical waste and lower production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If phosphoramidite techniques are used for de novo nucleic acid synthesis, then synthesis capability is provided, but high breakage rates and side reactions occur for long sequences
Solution Approach 1:
The patent modifies the chemical parameters of the synthesis system by replacing phosphoramidite reagents with engineered TdT enzymes and modified nucleotide analogs. This fundamental parameter change shifts the synthesis mechanism from chemical to enzymatic, enabling reliable synthesis of longer sequences without the breakage issues inherent in phosphoramidite chemistry
Solution Approach 2:
The patent substitutes the mechanical/chemical phosphoramidite synthesis system with a biological enzymatic system. The engineered TdT enzyme replaces the chemical phosphoramidite reagents and cyclization chemistry, providing a more reliable mechanism for forming phosphodiester bonds that scales to longer sequence lengths
2Productivity
If phosphoramidite synthesis is used, then nucleic acid synthesis is achieved, but toxic by-products are produced increasing disposal costs
Solution Approach 1:
The patent eliminates the harmful by-products of phosphoramidite synthesis by replacing the chemical synthesis pathway with an enzymatic one. The TdT enzyme catalyzes phosphodiester bond formation using nucleotide triphosphates, producing only pyrophosphate as a by-product, which is environmentally benign and easily disposed of, thus converting the harmful chemical waste problem into a clean biological process
Solution Approach 2:
The patent extracts and removes the toxic components from the synthesis system by eliminating phosphoramidite reagents, acetonitrile, and other hazardous chemicals. The system is reduced to aqueous buffers, enzymes, and modified nucleotide analogs, extracting the harmful elements while retaining the core synthesis functionality
3Productivity
If phosphoramidite synthesis is used, then oligonucleotide production is achieved, but costs increase due to waste disposal requirements
Solution Approach 1:
The patent converts the costly waste disposal requirement into a benefit by using an enzymatic system that produces minimal, non-toxic waste. The engineered TdT enzyme system eliminates the need for expensive hazardous waste disposal infrastructure and processes, reducing both direct disposal costs and indirect costs related to environmental compliance and facility requirements
4Adaptability or versatility
If native TdT enzymes are used for template-independent synthesis, then enzymatic synthesis is provided, but incorporation of blocked nucleotide analogs is inefficient or impossible
Solution Approach 1:
The patent applies local quality modification by making specific, targeted changes to the TdT enzyme structure at the molecular level. Through saturation mutagenesis and computational guidance, specific amino acid residues in the enzyme's active site are modified to accommodate the bulkier blocked nucleotide analogs, while maintaining the enzyme's overall structure and catalytic function
Solution Approach 2:
The patent changes the physical-chemical parameters of the enzyme by modifying its amino acid sequence to alter the properties of its substrate binding site. The engineered TdT variants have modified active site geometries and electrostatic properties that enable recognition and incorporation of 3′-O-blocked nucleotide analogs, fundamentally changing the enzyme's substrate specificity while maintaining catalytic efficiency
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
Enables the synthesis of longer polynucleotides with reduced chemical waste and lower costs, using a biological process that replaces chemical synthesis, facilitating the production of custom oligonucleotides with improved efficiency and environmental sustainability.
Implementation Method 1
Modified terminal deoxynucleotidyl transferase (TdT) enzymes that can incorporate 3′-O-blocked nucleotide analogs for template-independent synthesis
Implementation Method 2
nucleic acid synthesis using 3′-O-blocked nucleotide analogs and Shrimp Alkaline Phosphatase (SAP) for controlled addition of selected nucleotides
Data Source
AI summary
The invention includes methods for identifying polymerases, such as modified terminal nucleotidyl transferases (TdT), that are capable of binding nucleotides comprising removable 3′-O-blocking moieties to a nucleic acid initiator, without the use of a template. The invention further includes the identified polymerases, and methods of using the polymerases for de novo synthesis of predetermined oligonucleotide sequences.