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Novel Transaminase and Laccase from <i>Streptomyces</i> spp. Using Combined Identification Approaches
oleh: Erica E. Ferrandi, Jelena Spasic, Lidija Djokic, Yevhen Vainshtein, Ramsankar Senthamaraikannan, Sandra Vojnovic, Christian Grumaz, Daniela Monti, Jasmina Nikodinovic-Runic
Format: | Article |
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Diterbitkan: | MDPI AG 2021-07-01 |
Deskripsi
Three <i>Streptomyces</i> sp. strains with a multitude of target enzymatic activities confirmed by functional screening, namely BV129, BV286 and BV333, were subjected to genome sequencing aiming at the annotation of genes of interest, in-depth bioinformatics characterization and functional expression of the biocatalysts. A whole-genome shotgun sequencing followed by <i>de novo</i> genome assembly and annotation was performed revealing genomes of 6.4, 9.4 and 7.3 Mbp, respectively. Functional annotation of the proteins of interest resulted in between 2047 and 2763 putative targets. Among the various enzymatic activities that the three <i>Streptomyces</i> strains demonstrated to produce by functional screening, we focused our attention on transaminases (TAs) and laccases due to their high biocatalytic potential. Bioinformatics search allowed the identification of a putative TA from <i>Streptomyces</i> sp. BV333 as a potentially novel broad substrate scope TA and a putative laccase from <i>Streptomyces</i> sp. BV286 as potentially novel blue multicopper oxidase. The two sequences were cloned and overexpressed in <i>Escherichia coli</i> and the two novel enzymes, transaminase Sbv333-TA and laccase Sbv286-LAC, were characterized. Interestingly, both enzymes resulted to be exceptionally thermostable, Sbv333-TA showing a melting temperature (T<sub>M</sub> = 85 °C) only slightly lower compared to the T<sub>M</sub> of the most thermostable transaminases described to date (87–88 °C) and Sbv286-LAC being even thermoactivated at temperature >60 °C. Moreover, Sbv333-TA showed a broad substrate scope and remarkably demonstrated to be active in the transamination of β-ketoesters, which are rarely accepted by currently known TAs. On the other hand, Sbv286-LAC showed an improved activity in the presence of the cosolvent acetonitrile. Overall, it was shown that a combination of approaches from standard microbiological and biochemical screens to genome sequencing and analysis is required to afford novel and functional biocatalysts.