Glr, a glutamate racemase, supplies d-glutamate to both peptidoglycan synthesis and poly-γ-glutamate production in γ-PGA-producing Bacillus subtilis

• Published in: FEMS microbiology letters Vol. 236; no. 1; pp. 13 - 20
• Main Authors: Kada, Shigeki, Nanamiya, Hideaki, Kawamura, Fujio, Horinouchi, Sueharu
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier B.V 01.07.2004; Blackwell
• Subjects: Amino Acid Isomerases - genetics; Amino Acid Isomerases - metabolism; Bacillus subtilis; Bacillus subtilis - enzymology; Bacillus subtilis - growth & development; Biological and medical sciences; Cloning, Molecular; Food Microbiology; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Bacterial; Gene Expression Regulation, Enzymologic; Glutamate racemase; Glutamic Acid - metabolism; Microbiology; Mutagenesis; Peptidoglycan - biosynthesis; Phylogeny; Plasmids; Poly-γ-glutamate; Polyglutamic Acid - biosynthesis; Transcription, Genetic; Transcriptional analysis; Glutamate racemase; Transcriptional analysis; Bacillus subtilis; Poly-γ-glutamate; Peptidoglycan; Isomerases; Bacillales; Enzyme; Bacteria; Bacillaceae
• ISSN: 0378-1097; 1574-6968
• DOI: 10.1016/j.femsle.2004.05.028

Poly-γ-glutamate (γ-PGA)-producing Bacillus subtilis contains two glutamate racemase genes, glr and yrpC, as does γ-PGA-nonproducing B. subtilis strain 168. glr and yrpC on the chromosome of γ-PGA-producing strain r22 were separately disrupted by means of gene replacement with an erythromycin resistance determinant. yrpC-disruption caused no effects on growth or γ-PGA-production, whereas glr was disrupted only when an exogenous glr copy was present on a plasmid. In addition, the d-glutamate content of γ-PGA produced by the yrpC-disruptant was the same as that produced by the parental strain r22. Glr in strain r22 is therefore responsible for the supply of d-glutamate to the synthesis of both peptidoglycan and γ-PGA. Consistent with this idea, glr was transcribed actively during the exponential growth phase for peptidoglycan synthesis and continuously at a low, but distinct, level during the stationary phase for γ-PGA production, whereas yrpC was transcribed at a very low level throughout growth. Phylogenetic analysis of glutamate racemases from eubacteria showed that YrpC is distinct from other glutamate racemases.