AUTHOR=Ferrandi Erica Elisa , Sayer Christopher , De Rose Simone Antonio , Guazzelli Elisa , Marchesi Carlotta , Saneei Vahid , Isupov Michail N. , Littlechild Jennifer A. , Monti Daniela 

TITLE=New Thermophilic α/β Class Epoxide Hydrolases Found in Metagenomes From Hot Environments

JOURNAL=Frontiers in Bioengineering and Biotechnology

VOLUME=6

YEAR=2018

URL=https://www.frontiersin.org/journals/bioengineering-and-biotechnology/articles/10.3389/fbioe.2018.00144

DOI=10.3389/fbioe.2018.00144

ISSN=2296-4185

ABSTRACT=<p>Two novel epoxide hydrolases (EHs), Sibe-EH and CH65-EH, were identified in the metagenomes of samples collected in hot springs in Russia and China, respectively. The two α/β hydrolase superfamily fold enzymes were cloned, over-expressed in <italic>Escherichia coli</italic>, purified and characterized. The new EHs were active toward a broad range of substrates, and in particular, Sibe-EH was excellent in the desymmetrization of <italic>cis</italic>-2,3-epoxybutane producing the (2<italic>R</italic>,3<italic>R</italic>)-diol product with <italic>ee</italic> exceeding 99%. Interestingly these enzymes also hydrolyse (4<italic>R</italic>)-limonene-1,2-epoxide with Sibe-EH being specific for the <italic>trans</italic> isomer. The Sibe-EH is a monomer in solution whereas the CH65-EH is a dimer. Both enzymes showed high melting temperatures with the CH65-EH being the highest at 85°C retaining 80% of its initial activity after 3 h thermal treatment at 70°C making it the most thermal tolerant wild type epoxide hydrolase described. The Sibe-EH and CH65-EH have been crystallized and their structures determined to high resolution, 1.6 and 1.4 Å, respectively. The CH65-EH enzyme forms a dimer via its cap domains with different relative orientation of the monomers compared to previously described EHs. The entrance to the active site cavity is located in a different position in CH65-EH and Sibe-EH in relation to other known bacterial and mammalian EHs.</p>