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Lipase chemoselectivity - kinetics and applications
KTH, School of Biotechnology (BIO), Biochemistry.
2009 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

 

A chemoselective catalyst is preferred in a chemical reaction where protecting groups otherwise are needed. The two lipases Candida antarctica lipase B and Rhizomucor miehei lipase showed large chemoselectivity ratios, defined as (kcat/KM)OH / (kcat/KM)SH, in a transacylation reaction with ethyl octanoate as acyl donor and hexanol or hexanethiol as acyl acceptor (paper I). The chemoselectivity ratio of the uncatalyzed reaction was 120 in favour of the alcohol. Compared to the uncatalyzed reaction, the chemoselectivity was 730 times higher for Candida antarctica lipase B and ten times higher for Rhizomucor miehei lipase. The KM towards the thiol was more than two orders of magnitude higher than the KM towards the corresponding alcohol. This was the dominating contribution to the high chemoselectivity displayed by the two lipases. In a novel approach, Candida antarctica lipase B was used as catalyst for enzymatic synthesis of thiol-functionalized polyesters in a one-pot reaction without using protecting groups (paper II). Poly(e-caprolactone) with a free thiol at one of the ends was synthesized in an enzymatic ring-opening polymerization initiated with mercaptoethanol or terminated with either 3-mercaptopropionic acid or g-thiobutyrolactone.

 

Place, publisher, year, edition, pages
Stockholm: KTH , 2009. , 36 p.
Series
Trita-BIO-Report, ISSN 1654-2312 ; 2009:7
Keyword [en]
Candida antarctica lipase B, Rhizomucor miehei lipase, active site titration, kinetics, chemoselectivity, thiol, alcohol, thiol-functionalized polyesters
National Category
Biochemistry and Molecular Biology
Identifiers
URN: urn:nbn:se:kth:diva-10232ISBN: 978-91-7415-275-3 (print)OAI: oai:DiVA.org:kth-10232DiVA: diva2:211890
Presentation
2009-05-14, 10:00 (English)
Supervisors
Available from: 2009-05-06 Created: 2009-04-20 Last updated: 2010-10-13Bibliographically approved
List of papers
1. Lipase chemoselectivity towards alcohol and thiol acyl acceptors in a transacylation reaction
Open this publication in new window or tab >>Lipase chemoselectivity towards alcohol and thiol acyl acceptors in a transacylation reaction
2010 (English)In: Journal of Molecular Catalysis B: Enzymatic, ISSN 1381-1177, E-ISSN 1873-3158, Vol. 66, no 1-2, 120-123 p.Article in journal (Refereed) Published
Abstract [en]

The lipase chemoselectivity towards an alcohol and a thiol was investigated for the two lipases Candida antarctica lipase B (CalB) and Rhizomucor miehei lipase (Rml). Hexanol and hexanethiol were used as acyl acceptors in a transacylation reaction with ethyl octanoate in cyclohexane. CalB showed the highest chemoselectivity ratio (k(cat)/K-M)(OH)/(k(cat)/K-M)(SH), of 88,000 while the ratio for Rml was 1200. That could be compared with the ratio, k(OH)/k(SH), of 120 for the non-catalyzed reaction. Thus, the enzyme contribution to the chemoselectivity between hexanol and hexanethiol was 730 for CalB and 10 for Rml. High K-M values displayed towards hexanethiol (above 1.8 M) were the largest contribution to the selectivity. No saturation was achieved. The K-M values were more than two orders of magnitude higher than those of hexanol.

Keyword
Chemoselectiviry, Acylation, Lipase, Kinetics, Active site titration
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:kth:diva-25232 (URN)10.1016/j.molcatb.2010.04.005 (DOI)000280928200015 ()2-s2.0-77957827548 (Scopus ID)
Note
QC 20101013Available from: 2010-10-13 Created: 2010-10-13 Last updated: 2017-12-12Bibliographically approved
2. Thiol end-functionalization of poly(epsilon-caprolactone), catalyzed by Candida antarctica lipase B
Open this publication in new window or tab >>Thiol end-functionalization of poly(epsilon-caprolactone), catalyzed by Candida antarctica lipase B
Show others...
2005 (English)In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 38, no 3, 647-649 p.Article in journal (Refereed) Published
Abstract [en]

The use of Candida antarctica Lipase B (CALB) chemoselective catalyst in the Thiol End-Functionalization of Poly(ε-caprolacetone) was discussed. Thiol-functionalization of poly(ε-caprolacetone)(PCL) was made by an initiation reaction catalyzed by CALB in bulk. 2-Mercaptoethanol (1) was used to initiate the enzyme-assisted ring opening polymerization of ε-caprolacetone(2) to give the desired thiol-functionalized polymer. The structure of the terminated PCL was confirmed by 13C nuclear magnetic resonance .

Keyword
ring-opening polymerization, epsilon-caprolactone, polymers, monolayers, polyesters, surfaces
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:kth:diva-14502 (URN)10.1021/ma048056r (DOI)000226764500001 ()2-s2.0-13444258041 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved

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