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Molecular modeling studies of lipase-catalyzed β-lactam polymerization

  • I Baum
  • LA Haller
  • LW Schwab
  • K Loos
  • G Fels
Open Access
Poster presentation
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Keywords

Lipase Polyanilines Candida Polyphenol Copolymerization 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Enzymatic polymerization has emerged over the last 5 years as a field of considerable interest and commercial promise. The reaction proceeds with high regio-, enantio-, and chemoselectivity under relatively mild conditions. Enzymes have been used so far to synthesize polyesters, polysaccharides, polycarbonates, polyphenols, polyanilines, vinyl polymers, and poly-amino acids [1]. Particularly, lipase B of Candida antarctica immobilized on polyacrylic resin (Novozyme 435) has proven to be a very versatile catalyst and has successfully been used for the synthesis of polyesters from various substrates [2][3][4]. Little, however, has been reported on the enzyme catalyzed synthesis of polyamides [5].

While it has been shown that nylons can chemically be produced from the corresponding amino acids or by anionic ring-opening polymerization of 5–13 membered unsubstituted lactams, poly-β-alanine has not yet been obtained by either polymerization of β-alanine or β-lactam (2-azetidinone). Using lipase B of Candida antarctica we have recently been successful in the production of unbranched poly-βalanine starting from unsubstituted β-lactam [6].

Here we report preliminary molecular modeling studies of the lipase catalyzed ringopening polymerization of β-lactam towards an understanding of the underlying enzymatic mechanism. We can show that amide formation initially follows the well-known enzymatic acylation of Ser105 by β-lactam using Asp187 and His224 of the catalytic centre and Thr40 and Gly106 as oxy-anion hole. The elongation of the chain, however, utilizes different parts of the active site. The mechanism is only applicable for β-lactam and can not be utilized by β-alanine and suggests a reasoning for the experimental finding that β-alanine can not be polymerized enzymatically but rather inhibits the polymerization in a copolymerization experiment with β-lactam and β-alanine.

References

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Copyright information

© Baum et al; licensee BioMed Central Ltd. 2009

This article is published under license to BioMed Central Ltd.

Authors and Affiliations

  • I Baum
    • 1
  • LA Haller
    • 1
  • LW Schwab
    • 2
  • K Loos
    • 2
  • G Fels
    • 1
  1. 1.Department of ChemistryFaculty of Science, University of PaderbornPaderbornGermany
  2. 2.Department of Polymer Chemistry and Zernike Institute for Advanced MaterialsUniversity of GroningenGroningenThe Netherlands

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