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Alanine metabolism in Bacillus subtilis

Lookup NU author(s): Karzan Sidiq, Man Chow, Dr Victor Zhao, Dr Richard Daniel

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Abstract

© 2020 John Wiley & Sons Ltd. Both isomeric forms of alanine play a crucial role in bacterial growth and viability; the L-isomer of this amino acid is one of the building blocks for protein synthesis, and the D-isomer is incorporated into the bacterial cell wall. Despite a long history of genetic manipulation of Bacillus subtilis using auxotrophic markers, the genes involved in alanine metabolism have not been characterized fully. In this work, we genetically characterized the major enzymes involved in B. subtilis alanine biosynthesis and identified an alanine permease, AlaP (YtnA), which we show has a major role in the assimilation of D-alanine from the environment. Our results provide explanations for the puzzling fact that growth of B. subtilis does not result in the significant accumulation of extracellular D-alanine. Interestingly, we find that in B. subtilis, unlike E. coli where multiple enzymes have a biochemical activity that can generate alanine, the primary synthetic enzyme for alanine is encoded by alaT, although a second gene, dat, can support slow growth of an L-alanine auxotroph. However, our results also show that Dat mediates the synthesis of D-alanine and its activity is influenced by the abundance of L-alanine. This work provides valuable insights into alanine metabolism that suggests that the relative abundance of D- and L-alanine might be linked with cytosolic pool of D and L-glutamate, thereby coupling protein and cell envelope synthesis with the metabolic status of the cell. The results also suggest that, although some of the purified enzymes involved in alanine biosynthesis have been shown to catalyze reversible reactions in vitro, most of them function unidirectionally in vivo.


Publication metadata

Author(s): Sidiq KR, Chow MW, Zhao Z, Daniel RA

Publication type: Article

Publication status: Published

Journal: Molecular Microbiology

Year: 2021

Volume: 115

Issue: 4

Pages: 739-757

Print publication date: 01/04/2021

Online publication date: 06/11/2020

Acceptance date: 03/11/2020

ISSN (print): 0950-382X

ISSN (electronic): 1365-2958

Publisher: John Wiley & Sons Ltd

URL: https://doi.org/10.1111/mmi.14640

DOI: 10.1111/mmi.14640

PubMed id: 33155333


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