Nature versus nurture in two highly enantioselective esterases from Bacillus cereus and Thermoanaerobacter tengcongensis
Article first published online: 31 JUL 2009
© 2009 The Authors. Journal compilation © 2009 Society for Applied Microbiology and Blackwell Publishing Ltd
Special Issue: Biocatalysis. Guest Editors: Karl-Erich Jaeger, Andreas Schmid and Manuel Ferrer
Volume 3, Issue 1, pages 65–73, January 2010
How to Cite
Grosse, S., Bergeron, H., Imura, A., Boyd, J., Wang, S., Kubota, K., Miyadera, A., Sulea, T. and Lau, P. C. K. (2010), Nature versus nurture in two highly enantioselective esterases from Bacillus cereus and Thermoanaerobacter tengcongensis. Microbial Biotechnology, 3: 65–73. doi: 10.1111/j.1751-7915.2009.00142.x
- Issue published online: 20 DEC 2009
- Article first published online: 31 JUL 2009
- Received 5 June, 2009; accepted 3 July, 2009.
There is an increasing need for the use of biocatalysis to obtain enantiopure compounds as chiral building blocks for drug synthesis such as antibiotics. The principal findings of this study are: (i) the complete sequenced genomes of Bacillus cereus ATCC 14579 and Thermoanaerobacter tengcongensis MB4 contain a hitherto undescribed enantioselective and alkaliphilic esterase (BcEST and TtEST respectively) that is specific for the production of (R)-2-benzyloxy-propionic acid ethyl ester, a key intermediate in the synthesis of levofloxacin, a potent antibiotic; and (ii) directed evolution targeted for increased thermostability of BcEST produced two improved variants, but in either case the 3–5°C increase in the apparent melting temperature (Tm) of the mutants over the native BcEST that has a Tm of 50°C was outperformed by TtEST, a naturally occurring homologue with a Tm of 65°C. Protein modelling of BcEST mapped the S148C and K272R mutations at protein surface and the I88T and Q110L mutations at more buried locations. This work expands the repertoire of characterized members of the α/β-fold hydrolase superfamily. Further, it shows that genome mining is an economical option for new biocatalyst discovery and we provide a rare example of a naturally occurring thermostable biocatalyst that outperforms experimentally evolved homologues that carry out the same hydrolysis.