Atomistic Model for the Polyamide Formation from beta-Lactam Catalyzed by Candida antarctica Lipase B

Candida antarctica lipase B (CALB) is an established biocatalyst for a variety of transesterification, amidation, and polymerization. reactions. In contrast to polyesters, poly amides are not yet generally accessible via enzymatic polymerization. In this regard, an enzyme-catalyzed ring-opening poly...

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Bibliographic Details
Published in:ACS Catalysis
Main Authors: Baum, Iris, Elsaesser, Brigitta, Schwab, Leendert W., Loos, Katja, Fels, Gregor, Elsässer, Brigitta
Format: Article in Journal/Newspaper
Language:English
Published: 2011
Subjects:
Candida antarctica lipase B
enzyme catalysis
beta-lactam ring-opening
molecular modeling
enzymatic polymerization
enzyme acylation
RING-OPENING POLYMERIZATION
PROTEIN-LIGAND COMPLEXES
EPSILON-CAPROLACTONE
POLYESTERS
LACTONES
PREDICTION
RESOLUTION
MECHANISM
KINETICS
SOLVENT
Antarc*
Antarctica
Online Access:https://hdl.handle.net/11370/5eac70a5-1e8e-40fc-a3fe-db8c4337abfb
https://research.rug.nl/en/publications/5eac70a5-1e8e-40fc-a3fe-db8c4337abfb
https://doi.org/10.1021/cs1000398
https://pure.rug.nl/ws/files/6760998/2011ACSCatalBaum.pdf
Description
Summary:Candida antarctica lipase B (CALB) is an established biocatalyst for a variety of transesterification, amidation, and polymerization. reactions. In contrast to polyesters, poly amides are not yet generally accessible via enzymatic polymerization. In this regard, an enzyme-catalyzed ring-opening polymerization of beta-lactam (2-azetidinone) using CALB is the first example of an enzymatic polyamide formation yielding unbranched poly(beta-alanine), nylon 3. The performance of this polymerization, however, is poor, considering the maximum chain length of 18 monomer units with an average length of 8, and the molecular basis of the reaction so far is not understood. We have employed molecular modeling techniques using docking tools, molecular dynamics, and QM/MM procedures to gain insight into the mechanistic details of the various reaction steps involved. As a result, we propose a catalytic cycle for the oligomerization of beta-lactam that rationalizes the activation of the monomer, the chain elongation by additional beta-lactam molecules, and the termination of the polymer chain. In addition, the processes, leading to a premature chain termination are studied. Particularly, the QM/MM calculation enables an atomistic description of all eight steps involved in the catalytic cycle, which features an in situ-generated beta-alanine as the elongating monomer and which is compatible with the experimental findings.

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