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Applied and Environmental Microbiology, July 2004, p. 3941-3947, Vol. 70, No. 7
0099-2240/04/$08.00+0     DOI: 10.1128/AEM.70.7.3941-3947.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

Biodegradation of All Stereoisomers of the EDTA Substitute Iminodisuccinate by Agrobacterium tumefaciens BY6 Requires an Epimerase and a Stereoselective C-N Lyase

eljko Cokesa, Hans-Joachim Knackmuss, and Paul-Gerhard Rieger^*

Institut für Mikrobiologie, Universität Stuttgart, 70569 Stuttgart, Germany

Received 1 December 2003/ Accepted 2 April 2004

Biodegradation tests according to Organization for Economic Cooperation and Development standard 301F (manometric respirometry test) with technical iminodisuccinate (IDS) revealed ready biodegradability for all stereoisomers of IDS. The IDS-degrading strain Agrobacterium tumefaciens BY6 was isolated from activated sludge. The strain was able to grow on each IDS isomer as well as on Fe²⁺-, Mg²⁺-, and Ca²⁺-IDS complexes as the sole carbon, nitrogen, and energy source. In contrast, biodegradation of and growth on Mn²⁺-IDS were rather scant and very slow on Cu²⁺-IDS. Growth and turnover experiments with A. tumefaciens BY6 indicated that the isomer R,S-IDS is the preferred substrate. The IDS-degrading enzyme system isolated from this organism consists of an IDS-epimerase and a C-N lyase. The C-N lyase is stereospecific for the cleavage of R,S-IDS, generating D-aspartic acid and fumaric acid. The decisive enzyme for S,S-IDS and R,R-IDS degradation is the epimerase. It transforms S,S-IDS and R,R-IDS into R,S-IDS. Both enzymes do not require any cofactors. The two enzymes were purified and characterized, and the N-termini were sequenced. The purified lyase and also the epimerase catalyzed the transformation of alkaline earth metal-IDS complexes, while heavy metal-IDS complexes were transformed rather slowly or not at all. The observed mechanism for the complete mineralization of all IDS isomers involving an epimerase offers an interesting possibility of funneling all stereoisomers into a catabolic pathway initiated by a stereoselective lyase.

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* Corresponding author. Mailing address: Institut für Mikrobiologie, Universität Stuttgart, 70569 Stuttgart, Germany. Phone: 49-711-6855480. Fax: 49-711-6855725. E-mail: pg.rieger{at}po.uni-stuttgart.de.

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Applied and Environmental Microbiology, July 2004, p. 3941-3947, Vol. 70, No. 7
0099-2240/04/$08.00+0     DOI: 10.1128/AEM.70.7.3941-3947.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

This article has been cited by other articles:

• Bauerle, B., Cokesa, Z., Hofmann, S., Rieger, P.-G. (2006). Sequencing and Heterologous Expression of an Epimerase and Two Lyases from Iminodisuccinate-Degrading Bacteria. Appl. Environ. Microbiol. 72: 2824-2828 [Abstract] [Full Text]