Selective Enzymatic Amidation of Peptide C-Terminal Esters

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Solution Overview

Problem

Current methods for synthesizing peptides with a C-terminal amide function face challenges such as solubility issues, racemization, side reactions, and high costs due to the use of expensive enzymes, especially when trying to amidate C-terminal esters or acids in solution-phase synthesis.

Innovation Solution

The process involves using protease subtilisin in the presence of an ammonium salt derived from an acid with a pKa above 0 to amidate C-terminal esters or acids of peptide substrates, suppressing endopeptidase activity and achieving high yields while maintaining mild conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional enzymatic amidation methods are used, then amidation can be achieved, but the enzymes are expensive and have high endopeptidase activity that causes side reactions

Engineering Contradiction:

Improveselectivity of amidationVSAvoidendopeptidase activity causing side reactions

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent employs subtilisin, a protease enzyme that is more cost-effective and commercially available compared to expensive specialized amidating enzymes. While subtilisin has endopeptidase activity, this is managed through controlled reaction conditions, making it a practical disposable enzyme for the amidation process.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent optimizes reaction parameters including pH (maintained between 6-8 using phosphate buffer), temperature (30-40°C), and substrate concentration to suppress endopeptidase activity while promoting exopeptidase-mediated amidation. These parameter changes enable selective amidation despite using a protease with broad substrate specificity.

Inventive Principle:

Principle #35Parameter changes

2Stability of the object's composition

If C-terminal esters are used as starting materials, then solubility problems are avoided, but racemization and side reactions occur during amidation

Engineering Contradiction:

Improvesolubility of peptide substrateVSAvoidracemization of C-terminal amino acid

Core Design Contradiction:

Stability of the object's compositionVSManufacturing precision

Solution Approach 1:

The patent replaces harsh chemical amidation methods with enzymatic catalysis. The subtilisin enzyme catalyzes the amidation of C-terminal esters under mild physiological conditions (pH 6-8, 30-40°C), eliminating the need for strong bases or activating agents that cause racemization, while maintaining good solubility of the ester substrates.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If free C-terminal amide is maintained during synthesis, then the desired product is obtained, but solubility problems arise due to hydrogen bonding

Engineering Contradiction:

Improveformation of C-terminal amideVSAvoidsolubility of peptide chain

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent performs amidation as the final step after complete peptide assembly. The C-terminal ester is maintained throughout the synthesis steps, allowing the peptide chain to be built with good solubility. Only in the final step is the ester converted to the amide, ensuring the desired product is obtained without solubility issues during intermediate steps.

Inventive Principle:

Principle #10Preliminary action

4Ease of manufacture

If protease subtilisin is used for amidation, then cost is reduced and availability improved, but endopeptidase activity must be suppressed

Engineering Contradiction:

Improveavailability and cost of enzymeVSAvoidendopeptidase activity

Core Design Contradiction:

Ease of manufactureVSObject-generated harmful factors

Solution Approach 1:

The patent maintains reaction pH between 6-8 using phosphate buffer and temperature at 30-40°C, which optimizes subtilisin's exopeptidase activity for amidation while suppressing endopeptidase activity. These controlled parameters enable the use of this cost-effective, readily available enzyme without significant side reactions.

Inventive Principle:

Principle #35Parameter changes

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

This method allows for high-yield amidation of peptide substrates with minimal side reactions, overcoming previous limitations in solubility and enzyme cost, and is suitable for both protected and unprotected peptides in solution-phase synthesis.

Implementation Method 1

amidating one or more peptide substrates comprising C-terminal esters or acids using the protease subtilisin in any suitable form

Methodology Applied

Scientific EffectEnzymatic catalysis: Enzyme

Data Source

PatentUS8124372B2Selective enzymatic amidation of C-terminal esters or acids of peptides

Publication Date: 2012.02.28 MERCK SHARP & DOHME BV

AI summary

The present invention relates to a process for the amidation of C-terminal esters or acids of peptide substrates in solution-phase synthesis of peptides, comprising amidating one or more peptide substrates comprising C-terminal esters or acids using the protease subtilisin in any suitable form in the presence of an ammonium salt derived from an acid having a pKa above 0.This process is useful in the production of protected or unprotected peptides.