Thioesterase Decarboxylative Elimination for Terminal Alkene Synthesis

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Solution Overview

Problem

The synthesis of terminal alkenes in natural products like curacin A involves unique chemical steps, particularly the terminal alkene formation and the arrangement of domains in the hybrid polyketide synthase (PKS)/non-ribosomal peptide synthase (NRPS) pathway, which are not fully understood, especially the sulfotransferase (ST) and thioesterase (TE) domains involved in these processes.

Innovation Solution

A method is disclosed for preparing alkenes through decarboxylation of beta-sulfate carboxylic acids or carboxylic acid derivatives using a thioesterase (TE) that mediates decarboxylative elimination, where the beta-sulfate carboxylic acid or derivative is formed by sulfotransferase (ST) action on beta-hydroxy carboxylic acid derivatives, with specific amino acid sequences for the TE and ST ensuring enzymatic activity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional chemical synthesis methods are used for terminal alkene formation, then the reaction conditions are well-established, but the mechanism and domain arrangement in hybrid PKS/NRPS pathways remain mysterious and unelucidated

Engineering Contradiction:

Improvereaction mechanism understandingVSAvoidbiosynthetic pathway knowledge

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

The patent uses a sulfotransferase domain as an intermediary enzyme to introduce a sulfate group at the beta-position of the polyketide chain, creating a beta-sulfate carboxylic acid intermediate. This intermediary step enables subsequent decarboxylative elimination by the thioesterase domain to form the terminal alkene, thereby elucidating the previously mysterious biosynthetic mechanism through identifiable enzymatic intermediates and steps.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If the thioesterase domain performs standard hydrolysis or macrolactone formation, then the product is a carboxylic acid or macrolactone, but terminal alkene formation requires a unique decarboxylative elimination mechanism

Engineering Contradiction:

Improvethioesterase reaction capabilityVSAvoiddomain arrangement complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent demonstrates that the thioesterase domain has been locally modified or adapted to perform a specific function (decarboxylative elimination) distinct from the canonical functions of hydrolysis or macrolactone formation. This local functional specialization within the thioesterase domain enables terminal alkene production while maintaining the overall PKS module structure, resolving the contradiction between versatility and complexity.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The sulfotransferase domain performs a preliminary action by introducing a sulfate group at the beta-position before the thioesterase domain acts. This preliminary sulfation creates the necessary substrate configuration (beta-sulfate carboxylic acid) that enables the subsequent decarboxylative elimination reaction, allowing the thioesterase to achieve terminal alkene formation through a prepared intermediate state.

Inventive Principle:

Principle #10Preliminary action

3Quantity of substance

If the sulfotransferase introduces a sulfate group at the beta-position, then the beta-sulfate carboxylic acid intermediate is formed, but the decarboxylative elimination step requires specific enzymatic activity to proceed efficiently

Engineering Contradiction:

Improveterminal alkene yieldVSAvoidenzymatic reaction specificity

Core Design Contradiction:

Quantity of substanceVSManufacturing precision

Solution Approach 1:

The thioesterase domain performs a self-service function by utilizing its inherent nucleophilic attack capability (typically used for hydrolysis or lactonization) to instead attack the carbonyl carbon of the beta-sulfate carboxylic acid, triggering decarboxylation and forming the terminal alkene. The enzyme's existing structural features and catalytic mechanism are repurposed to serve the unique reaction requirement, achieving both high yield and specificity without requiring entirely new enzymatic machinery.

Inventive Principle:

Principle #25Self-service

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 effectively synthesizes terminal alkenes by decarboxylative elimination, elucidating the biochemical and structural insights into the CurM TE and ST domains, facilitating the production of natural products with terminal double bonds and offering tools for metabolic engineering.

Implementation Method 1

the TE mediates decarboxylative elimination of the beta-sulfate carboxylic acid or carboxylic acid derivative to form the alkene

Methodology Applied

Scientific EffectDecarboxylative elimination:

Implementation Method 2

the ST mediates the formation of the beta-sulfate carboxylic acid or carboxylic acid derivative

Methodology Applied

Scientific EffectSulfotransferase catalysis:

Data Source

PatentUS8765431B2Method for enzymatic production of decarboxylated polyketides and fatty acids

Publication Date: 2014.07.01 THE RGT UNIV OF MICHIGAN

AI summary

Disclosed herein are methods of preparing alkenes from beta-hydroxy or beta-sulfate carboxylic acid or carboxylic acid derivatives using thioesterase and optionally a sulfotransferase.