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  • 1.
    Engström, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Nyhlén, Jonas
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sandström, Anders G.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-Erling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Directed evolution of an enantioselective lipase with broad substrate scope for hydrolysis of α-substituted esters2010In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 132, no 20, p. 7038-7042Article in journal (Refereed)
    Abstract [en]

    A variant of Candida antarctica lipase A (CalA) was developed for the hydrolysis of α-substituted p-nitrophenyl esters by directed evolution. The E values of this variant for 7 different esters was 45−276, which is a large improvement compared to 2−20 for the wild type. The broad substrate scope of this enzyme variant is of synthetic use, and hydrolysis of the tested substrates proceeded with an enantiomeric excess between 95−99%. A 30-fold increase in activity was also observed for most substrates. The developed enzyme variant shows (R)-selectivity, which is reversed compared to the wild type that is (S)-selective for most substrates.

  • 2.
    Engström, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Nyhlén, Jonas
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sandström, Anders G.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-Erling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Enantioselective Kinetic Resolution of p-Nitrophenyl 2-Phenylpropanoate by a Variant of Candida antarctica Lipase A Developed by Directed Evolution2010In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 132, no 20, p. 7038-7042Article in journal (Refereed)
    Abstract [en]

    A variant of Candida antarctica lipase A (CalA) was developed for the hydrolysis of α-substituted p-nitrophenyl esters by directed evolution. The E values of this variant for 7 different esters was 45−276, which is a large improvement compared to 2−20 for the wild type. The broad substrate scope of this enzyme variant is of synthetic use, and hydrolysis of the tested substrates proceeded with an enantiomeric excess between 95−99%. A 30-fold increase in activity was also observed for most substrates. The developed enzyme variant shows (R)-selectivity, which is reversed compared to the wild type that is (S)-selective for most substrates.

  • 3.
    Ericsson, Daniel J.
    et al.
    1Department of Cell and Molecular Biology, Uppsala University, Biomedical Center.
    Kasrayan, Alex
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johansson, Patrik
    1Department of Cell and Molecular Biology, Uppsala University, Biomedical Center.
    Bergfors, Terese
    Department of Cell and Molecular Biology, Uppsala University, Biomedical Center.
    Sandström, Anders G.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-Erling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Mowbray, Sherry L.
    Department of Molecular Biology, Swedish University of Agricultural Sciences, Biomedical Center.
    X-Ray structure of Candida antarctica lipase A shows a novel lid structure and a likely mode of interfacial activation2008In: Journal of Molecular Biology, ISSN 0022-2836, Vol. 376, no 1, p. 109-119Article in journal (Refereed)
    Abstract [en]

    In nature, lipases (EC 3.1.1.3) catalyze the hydrolysis of triglycerides to form glycerol and fatty acids. Under the appropriate conditions, the reaction is reversible, and so biotechnological applications commonly make use of their capacity for esterification as well as for hydrolysis of a wide variety of compounds. In the present paper, we report the X-ray structure of lipase A from Candida antarctica, solved by single isomorphous replacement with anomalous scattering, and refined to 2.2-Å resolution. The structure is the first from a novel family of lipases. Contrary to previous predictions, the fold includes a well-defined lid as well as a classic α/β hydrolase domain. The catalytic triad is identified as Ser184, Asp334 and His366, which follow the sequential order considered to be characteristic of lipases; the serine lies within a typical nucleophilic elbow. Computer docking studies, as well as comparisons to related structures, place the carboxylate group of a fatty acid product near the serine nucleophile, with the long lipid tail closely following the path through the lid that is marked by a fortuitously bound molecule of polyethylene glycol. For an ester substrate to bind in an equivalent fashion, loop movements near Phe431 will be required, suggesting the primary focus of the conformational changes required for interfacial activation. Such movements will provide virtually unlimited access to solvent for the alcohol moiety of an ester substrate. The structure thus provides a basis for understanding the enzyme's preference for acyl moieties with long, straight tails, and for its highly promiscuous acceptance of widely different alcohol and amine moieties. An unconventional oxyanion hole is observed in the present structure, although the situation may change during interfacial activation

  • 4.
    Kasrayan, Alex
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bocola, Marco
    Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany.
    Sandström, Anders G.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lavén, Gaston
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-Erling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Prediction of the Candida antarctica lipase A protein structure by comparative modeling and site-directed mutagenesis2007In: ChemBioChem, ISSN 1439-4227, E-ISSN 1439-7633, Vol. 8, no 12, p. 1409-1415Article in journal (Refereed)
    Abstract [en]

    A number of model structures of the CalA suggested by comparative modeling were tested by site-directed mutagenesis. Enzyme variants were created where amino acids predicted to play key roles for the lipase activity in the different models were replaced by an inert amino acid (alanine). The results from activity measurements of the overproduced and purified mutant enzymes indicate a structure where the active site consists of amino acid residues Ser184, His366, and Asp334 and in which there is no lid. This model can be used for future targeted modifications of the enzyme to obtain new substrate acceptance, better thermostability, and higher enantioselectivity.

  • 5.
    Sandström, Anders
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Structural Determination and Directed Evolution of Candida antarctica Lipase A for Increased Enantioselectivity2009Licentiate thesis, comprehensive summary (Other academic)
  • 6.
    Sandström, Anders G.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Highly Combinatorial Reshaping of the Candida antarctica lipase A Substrate Pocket Using an Extremely Condensed LibraryManuscript (preprint) (Other academic)
    Abstract [en]

    A highly combinatorial structure based protein engineering method is demonstrated resulting in a thorough modification of the binding pocket of Candida antarctica lipase A (CALA). Nine amino acid sites surrounding the entire pocket were simultaneously mutated, contributing to a sculpting of the substrate pocket toward a sterically demanding substrate, an ibuprofen ester. The best variant was highly active and displayed remarkable increase in enantioselectivity toward the substrate, with an E-value of 101, compared to the wild type CALA that poor activity and possesses an E-value of 3.4. The potential mutations introduced were a highly reduced set of amino acids, containing only the wild type residue and an alternative residue, preferably a smaller one with similar properties. These minimal ‘binary’ sets allow for extremely condensed protein libraries. The choice of amino acid sites were based on a computer model, with the substrate forcibly bound in the active site. This highly combinatorial method can be used to obtain tailor-made enzymes that are active toward substrates that are not normally accepted by the enzyme. When multiple sites are altered simultaneously, there is a higher possibility of obtaining positive synergistic effects, and the protein fitness landscape is explored efficiently.

  • 7.
    Sandström, Anders G.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Protein Engineering of Candida antarctica Lipase A: Enhancing Enzyme Properties by Evolutionary and Semi-Rational Methods2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Enzymes are gaining increasing importance as catalysts for selective transformations in organic synthetic chemistry. The engineering and design of enzymes is a developing, growing research field that is employed in biocatalysis. In the present thesis, combinatorial protein engineering methods are applied for the development of Candida antarctica lipase A (CALA) variants with broader substrate scope and increased enantioselectivity. Initially, the structure of CALA was deduced by manual modelling and later the structure was established by X-ray crystallography. The elucidation of the structure of CALA revealed several biocatalytically interesting features. With the knowledge derived from the enzyme structure, enzyme variants were produced via iterative saturation mutagenesis (ISM), a powerful protein engineering approach. Several of these variants were highly active and enantioselective towards bulky esters. Furthermore, an extensively combinatorial protein engineering approach was developed and investigated. A CALA variant with a spacious substrate binding pocket that can accommodate an unusually bulky substrate, an ester derivate of the non-steroidal anti-inflammatory drug (S)-ibuprofen, was obtained with this approach.

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  • 8.
    Sandström, Anders G.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Engström, Karin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Nyhlén, Jonas
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kasrayan, Alex
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-Erling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Directed evolution of Candida antarctica lipase A using an episomaly replicating yeast plasmid2009In: Protein Engineering Design & Selection, ISSN 1741-0126, E-ISSN 1741-0134, Vol. 22, no 7, p. 413-420Article in journal (Refereed)
    Abstract [en]

    We herein report the first directed evolution of Candida antarctica lipase A (CalA), employing a combinatorial active-site saturation test (CAST). Wild-type CalA has a modest E-value of 5.1 in kinetic resolution of 4-nitrophenyl 2-methylheptanoate. Enzyme variants were expressed in Pichia pastoris by using the episomal vector pBGP1 which allowed efficient secretory expression of the lipase. Iterative rounds of CASTing yielded variants with good selectivity toward both the (S)- and the (R)-enantiomer. The best obtained enzyme variants had E-values of 52 (S) and 27 (R).

  • 9.
    Sandström, Anders G.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Wikmark, Ylva
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Engström, Karin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Nyhlén, Jonas
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Combinatorial reshaping of the Candida antarctica lipase A substrate pocket for enantioselectivity using an extremely condensed library2012In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 109, no 1, p. 78-83Article in journal (Refereed)
    Abstract [en]

    A highly combinatorial structure-based protein engineering method for obtaining enantioselectivity is reported that results in a thorough modification of the substrate binding pocket of Candida antarctica lipase A (CALA). Nine amino acid residues surrounding the entire pocket were simultaneously mutated, contributing to a reshaping of the substrate pocket to give increased enantioselectivity and activity for a sterically demanding substrate. This approach seems to be powerful for developing enantioselectivity when a complete reshaping of the active site is required. Screening toward ibuprofen ester 1, a substrate for which previously used methods had failed, gave variants with a significantly increased enantioselectivity and activity. Wild-type CALA has a moderate activity with an E value of only 3.4 toward this substrate. The best variant had an E value of 100 and it also displayed a high activity. The variation at each mutated position was highly reduced, comprising only the wild type and an alternative residue, preferably a smaller one with similar properties. These minimal binary variations allow for an extremely condensed protein library. With this highly combinatorial method synergistic effects are accounted for and the protein fitness landscape is explored efficiently.

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    Fulltext
  • 10.
    Shakeri, Mozaffar
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Engström, Karin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sandström, Anders G.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-Erling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Highly enantioselective resolution of β-amino esters by Candida antarctica lipase A immobilized in mesocellular foam: application to dynamic kinetic resolution2010In: ChemCatChem, ISSN 1867-3899, Vol. 2, no 5, p. 534-538Article in journal (Refereed)
    Abstract [en]

    Candida antarctica lipase A (CALA) immobilized in functionalized mesocellular foam in the presence of sucrose, followed by lyophilization, led to a dramatic increase in the enantioselectivity as well as an improved thermostability of the enzyme. The immobilized lipase was used for kinetic resolution (KR) and dynamic kinetic resolution (DKR) of the β-amino ester, ethyl 3-amino-3-phenylpropanoate. The temperature of optimum activity of CALA shifted from 20–30 °C to 80–90 °C on immobilization in the MCF. An “enantiomeric ratio” E (E=νA/νB; νA and νB are the rate constants for entantiomers A and B) of 69 and a conversion of 43 % in 1 h were obtained at 80 °C, whereas non-immobilized CALA lost its activity at T≥50 °C. The obtained immobilized CALA showed an E value of greater than 500 at 22 °C. Combination of the immobilized CALA with a ruthenium complex, acting as a racemization catalyst, allowed for a successful DKR of ethyl 3-amino-3-phenylpropanoate resulting in 85 % conversion and 89 % ee.

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