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Applied and Environmental Microbiology, May 2009, p. 3161-3170, Vol. 75, No. 10
0099-2240/09/$08.00+0     doi:10.1128/AEM.02705-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Exopolyphosphatases PPX1 and PPX2 from Corynebacterium glutamicum{triangledown}

Steffen N. Lindner,1,2,{dagger} Sandra Knebel,1,{dagger} Hendrik Wesseling,2,{dagger} Siegfried M. Schoberth,1 and Volker F. Wendisch2*

Institut für Biotechnologie 1, Forschungszentrum Jülich, D-52425 Jülich, Germany,1 Institute of Molecular Microbiology and Biotechnology, Westphalian Wilhelms University of Muenster, Muenster, Germany2

Received 26 November 2008/ Accepted 12 March 2009

Corynebacterium glutamicum accumulates up to 300 mM of inorganic polyphosphate (PolyP) in the cytosol or in granules. The gene products of cg0488 (ppx1) and cg1115 (ppx2) were shown to be active as exopolyphosphatases (PPX), as overexpression of either gene resulted in higher exopolyphosphatase activities in crude extracts and deletion of either gene with lower activities than those of the wild-type strain. PPX1 and PPX2 from C. glutamicum share only 25% identical amino acids and belong to different protein groups, which are distinct from enterobacterial, archaeal, and yeast exopolyphosphatases. In comparison to that in the wild type, more intracellular PolyP accumulated in the {Delta}ppx1 and {Delta}ppx2 deletion mutations but less when either ppx1 or ppx2 was overexpressed. When C. glutamicum was shifted from phosphate-rich to phosphate-limiting conditions, a growth advantage of the deletion mutants and a growth disadvantage of the overexpression strains compared to the wild type were observed. Growth experiments, exopolyphosphatase activities, and intracellular PolyP concentrations revealed PPX2 as being a major exopolyphosphatase from C. glutamicum. PPX2His was purified to homogeneity and shown to be active as a monomer. The enzyme required Mg2+ or Mn2+ cations but was inhibited by millimolar concentrations of Mg2+, Mn2+, and Ca2+. PPX2 from C. glutamicum was active with short-chain polyphosphates, even accepting pyrophosphate, and was inhibited by nucleoside triphosphates.

* Corresponding author. Mailing address: Institute of Molecular Microbiology and Biotechnology, Westphalian Wilhelms University of Muenster, Correnstr. 3, D-48149 Muenster, Germany. Phone: 49-251-833 9827. Fax: 49-251-833 8388. E-mail: wendisch{at}uni-muenster.de

{triangledown} Published ahead of print on 20 March 2009.

{dagger} Equal contributors.

Applied and Environmental Microbiology, May 2009, p. 3161-3170, Vol. 75, No. 10
0099-2240/09/$08.00+0     doi:10.1128/AEM.02705-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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