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J Bacteriol, June 1998, p. 3159-3165, Vol. 180, No. 12
Biotechnologie 1, Forschungszentrum
Jülich GmbH, D-52425 Jülich, Germany
Received 16 January 1998/Accepted 16 April 1998
In eubacteria, there are three slightly different pathways for the
synthesis of m-diaminopimelate (m-DAP), which is one of the
key linking units of peptidoglycan. Surprisingly, for unknown reasons,
some bacteria use two of these pathways together. An example is
Corynebacterium glutamicum, which uses both the succinylase and dehydrogenase pathways for m-DAP synthesis. In this study, we clone
dapD and prove by enzyme experiments that this gene encodes the succinylase (Mr = 24082), initiating the
succinylase pathway of m-DAP synthesis. By using gene-directed
mutation, dapD, as well as dapE encoding the
desuccinylase, was inactivated, thereby forcing C. glutamicum to use only the dehydrogenase pathway of m-DAP
synthesis. The mutants are unable to grow on organic nitrogen sources.
When supplied with low ammonium concentrations but excess carbon, their
morphology is radically altered and they are less resistant to
mechanical stress than the wild type. Since the succinylase has a high
affinity toward its substrate and uses glutamate as the nitrogen donor,
while the dehydrogenase has a low affinity and incorporates ammonium
directly, the m-DAP synthesis is another example of twin activities
present in bacteria for access to important metabolites such as the
well-known twin activities for the synthesis of glutamate or for the
uptake of potassium.
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Different Modes of Diaminopimelate Synthesis and
Their Role in Cell Wall Integrity: a Study with
Corynebacterium glutamicum
*
Corresponding author. Mailing address: Biotechnologie
1, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany.
Phone: 49 2461 61 5132. Fax: 49 2461 61 2710. E-mail:
l.eggeling{at}fz-juelich.de.
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