PAL-Catalyzed Protein Ligation with QC-Driven Stabilization
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Solution Overview
Problem
Current methods for protein ligation, particularly using peptidyl asparaginyl ligases (PALs), suffer from low catalytic efficiency and reversibility issues, requiring stoichiometric amounts of enzyme and excess nucleophiles for high-yielding reactions, especially in protein-protein ligation.
Innovation Solution
Coupling PAL-mediated ligation with glutaminyl cyclase (QC)-catalyzed pyroglutamyl formation to stabilize the ligation reaction by cyclizing the exposed glutamine residue, forming pyroglutamyl (pGlu), thereby increasing the yield of ligated products.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If PAL-mediated ligation is used for protein ligation, then ligation reaction can be achieved, but the reaction is reversible and requires excess nucleophile for high yield
Solution Approach 1:
The invention changes the chemical state of the P1' residue from glutamine (Q) to pyroglutamic acid (pGlu) through QC-catalyzed cyclization. This parameter change (chemical modification) transforms the reversible ligation reaction into an irreversible process, allowing high ligation yield without requiring excess nucleophile. The pGlu formation stabilizes the ligation product and prevents reverse reaction.
Solution Approach 2:
The invention implements a cascade enzymatic system where PAL performs ligation first, then QC immediately follows to cyclize the P1' residue. This continuous action sequence ensures the ligation product is stabilized in real-time, preventing reverse reaction and eliminating the need for excess nucleophile to drive the equilibrium forward.
2Productivity
If PAL-mediated ligation is used for protein ligation, then ligation reaction can be achieved, but stoichiometric amount of enzyme is required for practicable reaction
Solution Approach 1:
The invention changes the reaction irreversibility parameter by introducing QC-catalyzed pGlu formation. This parameter change allows the use of sub-stoichiometric enzyme amounts because the cascade system continuously drives the reaction forward through product stabilization, eliminating the need for stoichiometric enzyme to maintain high yield.
3Productivity
If sortase A is used for protein ligation, then ligation reaction can be achieved, but catalytic efficiency is low requiring stoichiometric enzyme
Solution Approach 1:
The invention uses PAL instead of sortase A, which represents a parameter change in enzyme selection with fundamentally different catalytic properties. PAL has much higher catalytic efficiency and, when combined with QC-catalyzed pGlu formation, enables sub-stoichiometric enzyme usage through irreversible product stabilization.
4Productivity
If transpeptidation is used for ligation, then ligation product is formed, but reversibility requires excess incoming nucleophile
Solution Approach 1:
The invention changes the reaction stability parameter by introducing QC-catalyzed cyclization of the P1' residue to pGlu. This parameter change converts the reversible transpeptidation reaction into an irreversible process, stabilizing the ligation product composition and eliminating the need for excess nucleophile to compensate for reversibility.
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
Achieves near-quantitative yields in protein-to-protein, protein-peptide, and peptide-peptide ligation with equal molar ratios, overcoming the reversibility and efficiency limitations of previous methods.
Implementation Method 1
PALs utilizes the catalytic cysteinyl thiol to cleave the Asn-P1' peptide bond in an acyl donor substrate, and the resultant asparaginyl thioester intermediate is then resolved by the amine nucleophile of an acyl acceptor substrate. Therefore, the ligation product is formed through transpeptidation.
Implementation Method 2
QC cyclizes P1' in the released P1'-P2' dipeptide motif to pyroglutamyl (pGlu).
Data Source
AI summary
The present invention generally relates to enzymatic peptide or protein ligation. In particular, the present invention provides an improved method of enzymatic peptide or protein ligation, which comprises coupling a peptidyl asparaginyl ligase (PAL)-catalyzed ligation to a glutaminyl cyclase (QC)-catalyzed pyroglutamyl formation to improve yield of ligated product.