Environmental roles of microbial amino acid racemases

Hernández, Sara B.; Cava, Felipe

doi:10.1111/1462-2920.13072

Cited by 74 publications

(49 citation statements)

References 165 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Microorganisms may also rebuild proteins directly from the necromass amino acids 29 . For this, D-amino acids need to be converted into L-forms by racemases 30 . The continuous reworking of the necromass pool pulls the sedimentary D:L-Asp ratio away from the equilibrium ratio that would otherwise result from pure abiotic racemization (Fig.…”

Section: Discussionmentioning

confidence: 99%

Microbial turnover times in the deep seabed studied by amino acid racemization modelling

Braun

Mhatre

Jaussi

et al. 2017

Sci Rep

View full text Add to dashboard Cite

The study of active microbial populations in deep, energy-limited marine sediments has extended our knowledge of the limits of life on Earth. Typically, microbial activity in the deep biosphere is calculated by transport-reaction modelling of pore water solutes or from experimental measurements involving radiotracers. Here we modelled microbial activity from the degree of D:L-aspartic acid racemization in microbial necromass (remains of dead microbial biomass) in sediments up to ten million years old. This recently developed approach (D:L-amino acid modelling) does not require incubation experiments and is highly sensitive in stable, low-activity environments. We applied for the first time newly established constraints on several important input parameters of the D:L-amino acid model, such as a higher aspartic acid racemization rate constant and a lower cell-specific carbon content of sub-seafloor microorganisms. Our model results show that the pool of necromass amino acids is turned over by microbial activity every few thousand years, while the turnover times of vegetative cells are in the order of years to decades. Notably, microbial turnover times in million-year-old sediment from the Peru Margin are up to 100-fold shorter than previous estimates, highlighting the influence of microbial activities on element cycling over geologic time scales.

show abstract

Section: Discussionmentioning

confidence: 99%

Microbial turnover times in the deep seabed studied by amino acid racemization modelling

Braun

Mhatre

Jaussi

et al. 2017

Sci Rep

View full text Add to dashboard Cite

show abstract

“…D-alanine is also released from the teichoic acids by spontaneous hydrolysis (16), consequently there should be an accumulation of free D-alanine residues in the vicinity of a growing cell unless actively re-assimilated by the bacterial cells. Pervious analyses of culture media composition after the growth of various bacterial species have revealed that many release D-amino acids on reaching stationary phase growth, presumably as secondary metabolites or signalling molecules (2). Indeed, stationary phase cultures of S. aureus have been shown to have significant levels of D-alanine present (1).…”

Section: Introductionmentioning

confidence: 99%

Alanine Metabolism inBacillus subtilis

Sidiq

Chow

Zhao

et al. 2019

Preprint

View full text Add to dashboard Cite

Despite a long history of genetic manipulation of Bacillus subtilis using auxotrophic markers in genetic manipulation, the genes involved in alanine metabolism have not been characterised fully. Here we show that B. subtilis expresses an alanine uptake permease, YtnA (DatA), that has a major role in the assimilation of D-alanine from the environment. Since this isomer of the amino acid is not normally abundant it likely source is form the cells own cell wall probably through the action of carboxypeptidases and/or the spontaneous release of D-alanine from the teichoic acids. Also in this work we clarify the synthetic pathways acting in the biosynthesis of alanine. Genetically we show that, unlike E. coli where multiple enzymes have a biochemical activity that can generate alanine, in B. subtilis the primary synthetic enzyme for alanine is encoded by alaT, although a second gene, dat, is present that can support slow growth of an alanine auxotroph however our data suggests that this enzyme probably synthesises D-alanine. In summary this work has provided an explanation of the observation that growth of B. subtilis is linked with an efficient recycling system for D-alanine that is released from the cell as the cell envelope is processed to permit cell enlargement. The results also suggest that the relative abundance of D- and L-alanine that might be linked with cytosolic pool of D and L-glutamate, and so enabling tight coupling protein and cell envelope synthesis with the metabolic status of the cell.

show abstract

“…Lysine decarboxylase is one of the PLP-dependent enzymes [5][6][7]. Therefore, the effect of PLP concentration in the reaction medium was examined.…”

Section: Characterization Of the Recombinant Lysine Decarboxylasementioning

confidence: 99%

Efficient Production of Enantiopure d-Lysine from l-Lysine by a Two-Enzyme Cascade System

Wang

Cao

et al. 2016

Catalysts

View full text Add to dashboard Cite

Abstract:The microbial production of D-lysine has been of great interest as a medicinal raw material. Here, a two-step process for D-lysine production from L-lysine by the successive microbial racemization and asymmetric degradation with lysine racemase and decarboxylase was developed. The whole-cell activities of engineered Escherichia coli expressing racemases from the strains Proteus mirabilis (LYR) and Lactobacillus paracasei (AAR) were first investigated comparatively. When the strain BL21-LYR with higher racemization activity was employed, L-lysine was rapidly racemized to give DL-lysine, and the D-lysine yield was approximately 48% after 0.5 h. Next, L-lysine was selectively catabolized to generate cadaverine by lysine decarboxylase. The comparative analysis of the decarboxylation activities of resting whole cells, permeabilized cells, and crude enzyme revealed that the crude enzyme was the best biocatalyst for enantiopure D-lysine production. The reaction temperature, pH, metal ion additive, and pyridoxal 5 -phosphate content of this two-step production process were subsequently optimized. Under optimal conditions, 750.7 mmol/L D-lysine was finally obtained from 1710 mmol/L L-lysine after 1 h of racemization reaction and 0.5 h of decarboxylation reaction. D-lysine yield could reach 48.8% with enantiomeric excess (ee) ≥ 99%.

show abstract

Environmental roles of microbial amino acid racemases

Cited by 74 publications

References 165 publications

Microbial turnover times in the deep seabed studied by amino acid racemization modelling

Microbial turnover times in the deep seabed studied by amino acid racemization modelling

Alanine Metabolism inBacillus subtilis

Efficient Production of Enantiopure d-Lysine from l-Lysine by a Two-Enzyme Cascade System

Contact Info

Product

Resources

About