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Molecular modeling studies of lipase-catalyzed β-lactam polymerization
Chemistry Central Journalvolume 3, Article number: P57 (2009)
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 . 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 . Little, however, has been reported on the enzyme catalyzed synthesis of polyamides .
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 .
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.
Kobayashi S, Ritter H, Kaplan D, eds: Enzyme-Catalyzed Synthesis of Polymers (Advances in Polmyer Science). 2007, Springer, Berlin
Thurecht KJ, Heise A, deGeus M, Villarroya S, Zhou JX, Wyatt MF, Howdle SM: Macromolecules. 2006, 39: 7967-10.1021/ma061310q.
Mee van der L, Helmich F, de Bruijn R, Vekemans JAJM, Palmans ARA, Meijer EW: Macromolecules. 2006, 39: 5021-10.1021/ma060668j.
Kumar A, Mei Y, Gross R: Macromolecules. 2003, 36: 5530-10.1021/ma025741u.
Gu Q-M, Maslanka WW, Cheng HN: Polym Prepr. 2006, 4: 234-
Schwab LW, Kroon R, Schouten AJ, Loos K: Macromol Rapid Commun. 2008, 29: 794-797. 10.1002/marc.200800117.