Conformational Selection in Enzyme-Catalyzed Depolymerization of Bio-based Polyesters

Area of Science:

• Biocatalysis and Polymer Science
• Sustainable Chemistry
• Biotechnology

Background:

• Enzymatic polymer degradation is crucial for a bio-based economy, but polymer bulkiness and chain conformations hinder biocatalyst efficiency.
• Previous work showed varying affinities of polyethylene terephthalate (PET) conformers to PETase, impacting depolymerization rates.
• Structural-function relationships in biopolymer biocatalysis remain poorly understood.

Purpose of the Study:

• To investigate the enzymatic biodegradation of novel bio-polyesters derived from a chiral terpene-based diol and renewable diesters.
• To explore the correlation between polymer chain conformation, enzyme active site binding, and depolymerization efficiency.
• To elucidate the role of conformational selection in optimizing biocatalytic degradation of biopolymers.

Main Methods:

• Synthesis of four bio-polyesters with varying semi-aromatic to aliphatic content.
• Enzymatic depolymerization using IsPETase S238A, Dura, and LCC enzymes.
• Induced-fit docking (IFD) analyses to predict substrate-enzyme conformational matches.

Main Results:

• Monomer yields from enzymatic depolymerization ranged from 2% to 17% without pre-treatment.
• Degradation efficiency strongly correlated with the degree of conformational matching between polymer chains and enzyme active sites, as predicted by IFD.
• This correlation held true irrespective of the reaction temperature.

Conclusions:

• Conformational selection is a critical factor in the enzymatic depolymerization of biopolymers.
• The specific conformation (straight or twisted) of a polymer chain significantly influences its affinity to enzyme ground-state conformers.
• Optimizing biocatalytic degradation requires careful consideration of the conformational compatibility between the polymer substrate and the enzyme, offering insights for sustainable bioprocess development.