Bioprospection of hydroxynitrile lyase activity in ferns and other non-commercialised plants in South Africa
Date
2019
Authors
Davids, Deidre
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Abstract
Hydroxynitrile lyases catalyse the decomposition of chiral cyanohydrins into a carbonyl compound and toxic hydrogen cyanide in vivo. The reverse reaction for the synthesis of chiral cyanohydrins, which are important precursors in the pharmaceutical, agrochemical and cosmetic industry, is desirable. This study aimed to discover novel hydroxynitrile lyase enzymes with superior biocatalytic properties to those currently used in industry by bioprospection using Feigl-Anger detection paper and novel hydrogen cyanide detection tubes. Forty-eight out of over 540 plant species (8.89%) were found to be cyanogenic. This is the first report of a hydroxynitrile lyase in the leaves of the African mulberry tree, Morus mesozygia, and in the fern family Thelypteridaceae. Hydroxynitrile lyases from three fern species namely, Thelypteris confluens, Davallia trichomanoides and Phlebodium aureum mandaianum were isolated and partially purified by anion exchange chromatography. Native polyacrylamide electrophoresis and an in-gel activity assay allowed for isolation of specific bands which were subjected to liquid chromatography tandem mass spectrometry. The hydroxynitrile lyase from T. confluens has good stability at pH 2.5 making it a promising candidate for industrial use, therefore, the transcriptome of TcHNL was generated. The integration of the peptide data and the transcriptome is currently underway and will lead to the elucidation of the amino acid sequence of the enzyme. This will allow for heterologous expression and further enzymatic characterisation studies on the enzyme to determine the feasibility of industrial application.
Keywords: Chiral cyanohydrins, blue native PAGE, clear native PAGE, hydrogen cyanide detection tubes, bioprospection, transcriptome
Description
A Dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science
27 May 2019, Johannesburg