( R )-Citramalate Synthase in Methanogenic Archaea

Howell, David M.; Xu, Huimin; White, Robert H.

doi:10.1128/jb.181.1.331-333.1999

Cited by 87 publications

(53 citation statements)

References 23 publications

(24 reference statements)

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“…4), or the citramalate cycle ( Fig. 5) (Howell et al, 1999;Dunfield et al, 2003;Theisen et al, 2005;Erb et al, 2007Erb et al, , 2009Berg & Ivanovsky, 2009;Peyraud et al, 2009;Alber, 2011;Khomyakova et al 2011). It is interesting that some intermediates of these assimilatory pathways, for example malate and glyoxylate, are also intermediates in the serine cycle and as such may afford easy coupling with utilization of the serine cycle.…”

Section: How Do Facultative Methanotrophs Assimilate Multicarbon Subsmentioning

confidence: 99%

Facultative methanotrophy: false leads, true results, and suggestions for future research

Semrau

DiSpirito

Vuilleumier

2011

FEMS Microbiol Lett

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Methanotrophs are a group of phylogenetically diverse microorganisms characterized by their ability to utilize methane as their sole source of carbon and energy. Early studies suggested that growth on methane could be stimulated with the addition of some small organic acids, but initial efforts to find facultative methanotrophs, i.e., methanotrophs able to utilize compounds with carbon-carbon bonds as sole growth substrates were inconclusive. Recently, however, facultative methanotrophs in the genera Methylocella, Methylocapsa, and Methylocystis have been reported that can grow on acetate, as well as on larger organic acids or ethanol for some species. All identified facultative methanotrophs group within the Alphaproteobacteria and utilize the serine cycle for carbon assimilation from formaldehyde. It is possible that facultative methanotrophs are able to convert acetate into intermediates of the serine cycle (e.g. malate and glyoxylate), because a variety of acetate assimilation pathways convert acetate into these compounds (e.g. the glyoxylate shunt of the tricarboxylic acid cycle, the ethylmalonyl-CoA pathway, the citramalate cycle, and the methylaspartate cycle). In this review, we summarize the history of facultative methanotrophy, describe scenarios for the basis of facultative methanotrophy, and pose several topics for future research in this area.

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Section: How Do Facultative Methanotrophs Assimilate Multicarbon Subsmentioning

confidence: 99%

Facultative methanotrophy: false leads, true results, and suggestions for future research

Semrau

DiSpirito

Vuilleumier

2011

FEMS Microbiol Lett

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“…NC_005791), which encodes 2-isopropylmalate synthase (IPMS), the first enzyme in the biosynthesis of leucine from 2-ketoisovalerate. Two ORFs, Mmp1018 and Mmp0153, appear to be orthologs of Methanocaldococcus jannaschii MJ1392 and MJ0503, involved (R)-citramalate and a-ketosuberate biosynthesis, respectively [15,16]. We made a mutation in the remaining ORF, Mmp1063, by replacing most of the gene with the pac (puromycin resistance) cassette ( Fig.…”

Section: Construction Of a Leucine-auxotrophic Mutantmentioning

confidence: 99%

Continuous culture of under defined nutrient conditions

Haydock¹,

Porat²,

Whitman³

et al. 2004

FEMS Microbiology Letters

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To study global regulation in the methanogenic archaeon Methanococcus maripaludis, we devised a system for steady-state growth in chemostats. New Brunswick Bioflo 110 bioreactors were equipped with controlled delivery of hydrogen, nitrogen, carbon dioxide, hydrogen sulfide, and anaerobic medium. We determined conditions and media compositions for growth with three different limiting nutrients, hydrogen, phosphate, and leucine. To investigate leucine limitation we constructed and characterized a mutant in the leuA gene for 2-isopropylmalate synthase, demonstrating for the first time the function of this gene in the Archaea. Steady state specific growth rates in these studies ranged from 0.042 to 0.24 h(-1). Plots of culture density vs. growth rate for each condition showed the behavior predicted by growth modeling. The results show that growth behavior is normal and reproducible and validate the use of the chemostat system for metabolic and global regulation studies in M. maripaludis.

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“…Besides the threonine pathway for isoleucine biosynthesis commonly found in bacteria and eukaryotic microorganisms, the alternative pyruvate pathway was originally observed in reversion experiments either with genetic mutations or under nonphysiological conditions (Kisumi et al, 1977). The first observation of isoleucine biosynthesis via pyruvate pathway under physiological conditions was made in an Archeae species, Methanobacterium thermoautotrophicum, and later supported by the cloning of the Methanobacterium jannaschii cimA gene and further characterization of its encoded CimA (Eikmanns et al, 1983;Howell et al, 1999). The complete identification of the pyruvate pathway in the pathogenic L. interrogans (Xu et al, 2004) not only proved the existence of this pathway under physiological conditions but also characterized all the biosynthetic enzymes involved.…”

Section: Discussionmentioning

confidence: 99%

“…Citramalate synthase (CimA) was assayed as described (Howell et al, 1999) with certain modifications. Samples to be assayed were brought to a final volume of 100 mL with TES buffer (0.1 M, pH 7.5), and made 1 mM each for acetyl-CoA and pyruvate.…”

Section: Enzyme Assaysmentioning

confidence: 99%

A comprehensive survey on isoleucine biosynthesis pathways in seven epidemicLeptospira interrogansreference strains of China

Zou

Guo

Picardeau

et al. 2007

FEMS Microbiology Letters

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Previous studies have indicated that different species of Leptospira synthesize isoleucine via either pyruvate and/or threonine pathways. Seven epidemic Leptospira interrogans reference strains from China belonging to different serovars, together with three saprophytic strains of Leptospira biflexa and Leptospira meyeri, were analysed. The isoleucine biosynthesis properties were studied firstly by measuring the key enzymes of the two pathways, citramalate synthase (CimA, CE4.1.3.-) and threonine deaminase (IlvA, CE4.2.1.16), from cell extracts of the bacteria. Meanwhile, alpha-isopropylmalate synthase (LeuA, CE4.2.1.12), the key enzyme of leucine biosynthesis, was also measured as a control. It was found that all L. interrogans strains synthesized isoleucine via the pyruvate pathway exclusively, but L. biflexa and L. meyeri used both pathways. Dot-Blot and PCR amplification of both cimA and ilvA genes in the corresponding strains provided additional evidence consistent with the data of enzymatic assays. Although it is evident that leptospires' isoleucine biosynthesis may preferentially adapt either to the pyruvate pathway exclusively for pathogens or to the combination of both pyruvate and threonine pathways for saprophytes, broader sampling with careful genomospecies identification is needed for a solid conclusion.

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( R )-Citramalate Synthase in Methanogenic Archaea

Cited by 87 publications

References 23 publications

Facultative methanotrophy: false leads, true results, and suggestions for future research

Facultative methanotrophy: false leads, true results, and suggestions for future research

Continuous culture of under defined nutrient conditions

A comprehensive survey on isoleucine biosynthesis pathways in seven epidemicLeptospira interrogansreference strains of China

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