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Rational engineering of an esterase/acyltransferase for improved amidase specificity in amide synthesis and hydrolysis
KTH, School of Biotechnology (BIO), Industrial Biotechnology.ORCID iD: 0000-0001-9001-9271
KTH, School of Biotechnology (BIO), Industrial Biotechnology.ORCID iD: 0000-0003-2644-0752
KTH, School of Biotechnology (BIO), Industrial Biotechnology.ORCID iD: 0000-0002-2993-9375
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The esterase/acyltransferase from Mycobacterium smegmatis, MsAcT, display high acyltransfer capacity in water media with demonstrations found for both ester and amide syntheses. However, it has recently been discovered that esterases in contrast to amidases lack a key hydrogen bond in the transition state, donated by the scissile NH-group of the substrate. Esterases with improved amidase performance have been achieved with the introduction of amino-acid side chains or water network as hydrogen bond acceptors. Using the esterase from Mycobacterium smegmatis, MsAcT, the influence of this hydrogen bond was studied in both amide hydrolysis and synthesis, using a rational engineering approach. Two positions were selected for mutagenesis and enzyme variants with improved performance in amide synthesis and hydrolysis were generated. Compared to the wild-type, variant F154A had the highest absolute increase in amidase specificity (11-fold) and I194Q had the greatest change in relative amidase versus esterase reaction specificity (160-fold). The relative reaction specificities for amide over ester synthesis followed a similar trend as that of hydrolysis and the best variant was I194Q with a 32-fold increase compared to wt. Based on MD-simulations water seems to play an important role in the transition state as a hydrogen bond bridge between the NH-group of the amide substrate and the enzyme.

National Category
Biocatalysis and Enzyme Technology
Research subject
Biotechnology
Identifiers
URN: urn:nbn:se:kth:diva-196891OAI: oai:DiVA.org:kth-196891DiVA: diva2:1049537
Note

QC 20161129

Available from: 2016-11-24 Created: 2016-11-24 Last updated: 2016-11-29Bibliographically approved
In thesis
1. Rational engineering of esterases for improved amidase specificity in amide synthesis and hydrolysis
Open this publication in new window or tab >>Rational engineering of esterases for improved amidase specificity in amide synthesis and hydrolysis
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Biocatalysis is an ever evolving field that uses enzymes or microorganisms for chemical synthesis. By utilizing enzymes that generally have evolved for specific reactions under mild conditions and temperatures, biocatalysis can be a more environmentally friendly option compared to traditional chemistry.

Amide-type chemistries are important and bond formation avoiding poor atom economy is of high priority in organic chemistry. Biocatalysis could potentially be a solution but restricted substrate scope is a limitation. Esterases/lipases usually display broad substrate scope and catalytic promiscuity but are poor at hydrolyzing amides compared to amidases/proteases. The difference between the two enzyme classes is hypothesized to reside in one key hydrogen bond present in amidases, which facilitates the transition state for nitrogen inversion during catalysis.

In this thesis the work has been focused on introducing a stabilizing hydrogen bond acceptor in esterases, mimicking that found in amidases, to develop better enzymatic catalysts for amide-based chemistries.

By two strategies, side-chain or water interaction, variants were created in three esterases that displayed up to 210-times increased relative amidase specificity compared to the wild type. The best variant displayed reduced activation enthalpy corresponding to a weak hydrogen bond. The results show an estimated lower limit on how much the hydrogen bond can be worth to catalysis.

MsAcT catalyze kinetically controlled N-acylations in water. An enzymatic one-pot one-step cascade was developed for the formation of amides from aldehydes in water that gave 97% conversion. In addition, engineered variants of MsAcT with increased substrate scope could synthesize an amide in water with 81% conversion, where the wild type gave no conversion. Moreover, variants of MsAcT displayed up to 32-fold change in specificity towards amide synthesis and a switch in reaction preference favoring amide over ester synthesis.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. 76 p.
Series
TRITA-BIO-Report, ISSN 1654-2312 ; 2016:21
Keyword
Amidase, Biocatalysis, Enzyme, Esterase, Enzyme engineering, Lipase, Substrate specificity
National Category
Biocatalysis and Enzyme Technology
Research subject
Biotechnology
Identifiers
urn:nbn:se:kth:diva-196892 (URN)978-91-7729-210-4 (ISBN)
Public defence
2016-12-16, FD5, AlbaNova University Center, Roslagstullsbacken 21, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20161125

Available from: 2016-11-25 Created: 2016-11-24 Last updated: 2016-11-25Bibliographically approved

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