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Glutamate dehydrogenase and glutamine synthetase are regulated in response to nitrogen availability in Myocbacterium smegmatis
BACKGROUND: The assimilation of nitrogen is an essential process in all prokaryotes, yet a relatively limited amount of information is available on nitrogen metabolism in the mycobacteria. The physiological role and pathogenic properties of glutamine synthetase (GS) have been extensively investigate...
Autores principales: | , , , , |
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Formato: | Texto |
Lenguaje: | English |
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BioMed Central
2010
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2881912/ https://www.ncbi.nlm.nih.gov/pubmed/20459763 http://dx.doi.org/10.1186/1471-2180-10-138 |
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author | Harper, Catriona J Hayward, Don Kidd, Martin Wiid, Ian van Helden, Paul |
author_facet | Harper, Catriona J Hayward, Don Kidd, Martin Wiid, Ian van Helden, Paul |
author_sort | Harper, Catriona J |
collection | PubMed |
description | BACKGROUND: The assimilation of nitrogen is an essential process in all prokaryotes, yet a relatively limited amount of information is available on nitrogen metabolism in the mycobacteria. The physiological role and pathogenic properties of glutamine synthetase (GS) have been extensively investigated in Mycobacterium tuberculosis. However, little is known about this enzyme in other mycobacterial species, or the role of an additional nitrogen assimilatory pathway via glutamate dehydrogenase (GDH), in the mycobacteria as a whole. We investigated specific enzyme activity and transcription of GS and as well as both possible isoforms of GDH (NAD(+)- and NADP(+)-specific GDH) under varying conditions of nitrogen availability in Mycobacterium smegmatis as a model for the mycobacteria. RESULTS: It was found that the specific activity of the aminating NADP(+)-GDH reaction and the deaminating NAD(+)-GDH reaction did not change appreciably in response to nitrogen availability. However, GS activity as well as the deaminating NADP(+)-GDH and aminating NAD(+)-GDH reactions were indeed significantly altered in response to exogenous nitrogen concentrations. Transcription of genes encoding for GS and the GDH isoforms were also found to be regulated under our experimental conditions. CONCLUSIONS: The physiological role and regulation of GS in M. smegmatis was similar to that which has been described for other mycobacteria, however, in our study the regulation of both NADP(+)- and NAD(+)-GDH specific activity in M. smegmatis appeared to be different to that of other Actinomycetales. It was found that NAD(+)-GDH played an important role in nitrogen assimilation rather than glutamate catabolism as was previously thought, and is it's activity appeared to be regulated in response to nitrogen availability. Transcription of the genes encoding for NAD(+)-GDH enzymes seem to be regulated in M. smegmatis under the conditions tested and may contribute to the changes in enzyme activity observed, however, our results indicate that an additional regulatory mechanism may be involved. NADP(+)-GDH seemed to be involved in nitrogen assimilation due to a constitutive aminating activity. The deaminating reaction, however was observed to change in response to varying ammonium concentrations which suggests that NADP(+)-GDH is also regulated in response to nitrogen availability. The regulation of NADP(+)-GDH activity was not reflected at the level of gene transcription thereby implicating post-transcriptional modification as a regulatory mechanism in response to nitrogen availability. |
format | Text |
id | pubmed-2881912 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2010 |
publisher | BioMed Central |
record_format | MEDLINE/PubMed |
spelling | pubmed-28819122010-06-08 Glutamate dehydrogenase and glutamine synthetase are regulated in response to nitrogen availability in Myocbacterium smegmatis Harper, Catriona J Hayward, Don Kidd, Martin Wiid, Ian van Helden, Paul BMC Microbiol Research article BACKGROUND: The assimilation of nitrogen is an essential process in all prokaryotes, yet a relatively limited amount of information is available on nitrogen metabolism in the mycobacteria. The physiological role and pathogenic properties of glutamine synthetase (GS) have been extensively investigated in Mycobacterium tuberculosis. However, little is known about this enzyme in other mycobacterial species, or the role of an additional nitrogen assimilatory pathway via glutamate dehydrogenase (GDH), in the mycobacteria as a whole. We investigated specific enzyme activity and transcription of GS and as well as both possible isoforms of GDH (NAD(+)- and NADP(+)-specific GDH) under varying conditions of nitrogen availability in Mycobacterium smegmatis as a model for the mycobacteria. RESULTS: It was found that the specific activity of the aminating NADP(+)-GDH reaction and the deaminating NAD(+)-GDH reaction did not change appreciably in response to nitrogen availability. However, GS activity as well as the deaminating NADP(+)-GDH and aminating NAD(+)-GDH reactions were indeed significantly altered in response to exogenous nitrogen concentrations. Transcription of genes encoding for GS and the GDH isoforms were also found to be regulated under our experimental conditions. CONCLUSIONS: The physiological role and regulation of GS in M. smegmatis was similar to that which has been described for other mycobacteria, however, in our study the regulation of both NADP(+)- and NAD(+)-GDH specific activity in M. smegmatis appeared to be different to that of other Actinomycetales. It was found that NAD(+)-GDH played an important role in nitrogen assimilation rather than glutamate catabolism as was previously thought, and is it's activity appeared to be regulated in response to nitrogen availability. Transcription of the genes encoding for NAD(+)-GDH enzymes seem to be regulated in M. smegmatis under the conditions tested and may contribute to the changes in enzyme activity observed, however, our results indicate that an additional regulatory mechanism may be involved. NADP(+)-GDH seemed to be involved in nitrogen assimilation due to a constitutive aminating activity. The deaminating reaction, however was observed to change in response to varying ammonium concentrations which suggests that NADP(+)-GDH is also regulated in response to nitrogen availability. The regulation of NADP(+)-GDH activity was not reflected at the level of gene transcription thereby implicating post-transcriptional modification as a regulatory mechanism in response to nitrogen availability. BioMed Central 2010-05-11 /pmc/articles/PMC2881912/ /pubmed/20459763 http://dx.doi.org/10.1186/1471-2180-10-138 Text en Copyright ©2010 Harper et al; licensee BioMed Central Ltd. http://creativecommons.org/licenses/by/2.0 This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. |
spellingShingle | Research article Harper, Catriona J Hayward, Don Kidd, Martin Wiid, Ian van Helden, Paul Glutamate dehydrogenase and glutamine synthetase are regulated in response to nitrogen availability in Myocbacterium smegmatis |
title | Glutamate dehydrogenase and glutamine synthetase are regulated in response to nitrogen availability in Myocbacterium smegmatis |
title_full | Glutamate dehydrogenase and glutamine synthetase are regulated in response to nitrogen availability in Myocbacterium smegmatis |
title_fullStr | Glutamate dehydrogenase and glutamine synthetase are regulated in response to nitrogen availability in Myocbacterium smegmatis |
title_full_unstemmed | Glutamate dehydrogenase and glutamine synthetase are regulated in response to nitrogen availability in Myocbacterium smegmatis |
title_short | Glutamate dehydrogenase and glutamine synthetase are regulated in response to nitrogen availability in Myocbacterium smegmatis |
title_sort | glutamate dehydrogenase and glutamine synthetase are regulated in response to nitrogen availability in myocbacterium smegmatis |
topic | Research article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2881912/ https://www.ncbi.nlm.nih.gov/pubmed/20459763 http://dx.doi.org/10.1186/1471-2180-10-138 |
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