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Applied and Environmental Microbiology, December 2005, p. 8514-8518, Vol. 71, No. 12
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.12.8514-8518.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Enantioselective Transformation of {alpha}-Hexachlorocyclohexane by the Dehydrochlorinases LinA1 and LinA2 from the Soil Bacterium Sphingomonas paucimobilis B90A

Mrutyunjay Suar,1,5 Andrea Hauser,2 Thomas Poiger,2 Hans-Rudolf Buser,2 Markus D. Müller,2 Charu Dogra,1 Vishakha Raina,1 Christof Holliger,3 Jan Roelof van der Meer,4 Rup Lal,1 and Hans-Peter E. Kohler5*

Department of Zoology, University of Delhi, Delhi-110007, India,1 Swiss Federal Research Station (FAW), CH-8820 Wädenswil, Switzerland,2 EPFL, ENAC-ISTE, Laboratory for Environmental Biotechnology, CH-1015 Lausanne, Switzerland,3 Department of Fundamental Microbiology, University of Lausanne, CH-1015 Lausanne, Switzerland,4 Swiss Federal Institute of Aquatic Research and Technology (Eawag), CH-8600 Dübendorf, Switzerland5

Received 14 June 2005/ Accepted 9 September 2005

Sphingomonas paucimobilis B90A contains two variants, LinA1 and LinA2, of a dehydrochlorinase that catalyzes the first and second steps in the metabolism of hexachlorocyclohexanes (R. Kumari, S. Subudhi, M. Suar, G. Dhingra, V. Raina, C. Dogra, S. Lal, J. R. van der Meer, C. Holliger, and R. Lal, Appl. Environ. Microbiol. 68:6021-6028, 2002). On the amino acid level, LinA1 and LinA2 were 88% identical to each other, and LinA2 was 100% identical to LinA of S. paucimobilis UT26. Incubation of chiral {alpha}-hexachlorocyclohexane ({alpha}-HCH) with Escherichia coli BL21 expressing functional LinA1 and LinA2 S-glutathione transferase fusion proteins showed that LinA1 preferentially converted the (+) enantiomer, whereas LinA2 preferred the (–) enantiomer. Concurrent formation and subsequent dissipation of ß-pentachlorocyclohexene enantiomers was also observed in these experiments, indicating that there was enantioselective formation and/or dissipation of these enantiomers. LinA1 preferentially formed (3S,4S,5R,6R)-1,3,4,5,6-pentachlorocyclohexene, and LinA2 preferentially formed (3R,4R,5S,6S)-1,3,4,5,6-pentachlorocyclohexene. Because enantioselectivity was not observed in incubations with whole cells of S. paucimobilis B90A, we concluded that LinA1 and LinA2 are equally active in this organism. The enantioselective transformation of chiral {alpha}-HCH by LinA1 and LinA2 provides the first evidence of the molecular basis for the changed enantiomer composition of {alpha}-HCH in many natural environments. Enantioselective degradation may be one of the key processes determining enantiomer composition, especially when strains that contain only one of the linA genes, such as S. paucimobilis UT26, prevail.

* Corresponding author. Mailing address: Department of Environmental Microbiology, Swiss Federal Institute of Aquatic Science and Technology (Eawag), Ueberlandstrasse 133, P.O. Box 611, CH-8600 Dübendorf, Switzerland. Phone: 41 823 5521. Fax: 41 0182 35547. E-mail: kohler{at}eawag.ch.

Applied and Environmental Microbiology, December 2005, p. 8514-8518, Vol. 71, No. 12
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.12.8514-8518.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Sharma, P., Raina, V., Kumari, R., Malhotra, S., Dogra, C., Kumari, H., Kohler, H.-P. E., Buser, H.-R., Holliger, C., Lal, R. (2006). Haloalkane Dehalogenase LinB Is Responsible for {beta}- and {delta}-Hexachlorocyclohexane Transformation in Sphingobium indicum B90A. Appl. Environ. Microbiol. 72: 5720-5727 [Abstract] [Full Text]  


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