Different modes of diaminopimelate synthesis and their role in cell wall integrity: a study with Corynebacterium glutamicum.
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 (M(r) = 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.
Wehrmann
A
A
Forschungszentrum Jülich GmbH, Germany.
Phillipp
B
B
Sahm
H
H
Eggeling
L
L
D000217:Acyltransferases / Q000235:genetics / Q000378:metabolism; D000581:Amidohydrolases / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000378:metabolism; D001483:Base Sequence; D002473:Cell Wall / Q000378:metabolism*; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D003352:Corynebacterium / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D017931:DNA Primers / Q000235:genetics; D003960:Diaminopimelic Acid / Q000378:metabolism*; D005798:Genes, Bacterial; D008855:Microscopy, Electron, Scanning; D008969:Molecular Sequence Data; D009154:Mutation; D010457:Peptidoglycan / Q000096:biosynthesis; D010641:Phenotype; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D000217:Acyltransferases; D000581:Amidohydrolases; D000596:Amino Acids; D017931:DNA Primers; D003960:Diaminopimelic Acid; D010457:Peptidoglycan; D000644:Quaternary Ammonium Compounds; C040777:succinyl-CoA-tetrahydrodipicolinate N-succinyltransferase; C054685:N-succinyl-l,l-diaminopimelic acid desuccinylase