Biochemical studies of the multicopper oxidase (small laccase) from S treptomyces coelicolor using bioactive phytochemicals and site‐directed mutagenesis
| Autor: | Greg Brown, Robert Flick, Mamdouh Abou-Zaid, Emma R. Master, Mohammed Sherif, Valentina Mavisakalyan, Bihter Korbeci, Alexander F. Yakunin, Debbie Waung |
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| Rok vydání: | 2013 |
| Předmět: |
Phytochemicals
Coenzymes Streptomyces coelicolor Bioengineering Multicopper oxidase Applied Microbiology and Biotechnology Biochemistry Substrate Specificity Ferulic acid 03 medical and health sciences chemistry.chemical_compound Enzyme Stability Caffeic acid 030304 developmental biology Thermostability Laccase 0303 health sciences Oxidase test biology 030302 biochemistry & molecular biology Temperature Hydrogen-Ion Concentration biology.organism_classification Kinetics chemistry Mutagenesis Site-Directed Myricetin Oxidoreductases Copper Research Article Biotechnology |
| Zdroj: | Microbial Biotechnology |
| ISSN: | 1751-7915 |
| DOI: | 10.1111/1751-7915.12068 |
| Popis: | Summary Multicopper oxidases can act on a broad spectrum of phenolic and non-phenolic compounds. These enzymes include laccases, which are widely distributed in plants and fungi, and were more recently identified in bacteria. Here, we present the results of biochemical and mutational studies of small laccase (SLAC), a multicopper oxidase from Streptomyces coelicolor (SCO6712). In addition to typical laccase substrates, SLAC was tested using phenolic compounds that exhibit antioxidant activity. SLAC showed oxidase activity against 12 of 23 substrates tested, including caffeic acid, ferulic acid, resveratrol, quercetin, morin, kaempferol and myricetin. The kinetic parameters of SLAC were determined for 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid), 2,6-dimethoxyphenol, quercetin, morin and myricetin, and maximum reaction rates were observed with myricetin, where kcat and Km values at 60°C were 8.1 (± 0.8) s−1 and 0.9 (± 0.3) mM respectively. SLAC had a broad pH optimum for activity (between pH 4 and 8) and temperature optimum at 60–70°C. It demonstrated remarkable thermostability with a half-life of over 10 h at 80°C and over 7 h at 90°C. Site-directed mutagenesis revealed 17 amino acid residues important for SLAC activity including the 10 His residues involved in copper coordination. Most notably, the Y229A and Y230A mutant proteins showed over 10-fold increase in activity compared with the wild-type SLAC, which was correlated to higher copper incorporation, while kinetic analyses with S929A predicts localization of this residue near the meta-position of aromatic substrates. Funding Information Funding for this research was provided by the Government of Ontario for the project ‘FFABnet: Functionalized Fibre and Biochemicals’ (ORF-RE-05-005), and the Natural Sciences and Engineering Research Council of Canada. |
| Databáze: | OpenAIRE |
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