The Acetate Switch

Wolfe, Alan J.

doi:10.1128/mmbr.69.1.12-50.2005

Cited by 1,066 publications

(1,353 citation statements)

References 493 publications

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“…the ammonia concentration remained constant at 0.41 g L for 25 h followed by an increase to 0.55 g L . Both H. volcanii cultures formed acetate, which has an expression-and growthreducing effect (Braesen and Schoenheit 2001 ;Wolfe 2005 ), yet in the case of ADH/D1, the maximum concentration of 0.12 g L dropped to 0.08 g L at harvest time. In contrast, the formation of high acetate levels (with a constant increase to 0.28 g L ) accompanied ADH/A1 expression and ammonia accumulated to a high concentration of up to 0.70 g L (Fig.…”

Section: Discussionmentioning

confidence: 99%

Production of halophilic proteins using Haloferax volcanii H1895 in a stirred-tank bioreactor

Strillinger

Grötzinger

Allers

et al. 2015

Appl Microbiol Biotechnol

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The success of biotechnological processes is based on the availability of efficient and highly specific biocatalysts, which can satisfy industrial demands. Extreme and remote environments like the deep brine pools of the Red Sea represent highly interesting habitats for the discovery of novel halophilic and thermophilic enzymes. Haloferax volcanii constitutes a suitable expression system for halophilic enzymes obtained from such brine pools. We developed a batch process for the cultivation of H. volcanii H1895 in controlled stirred-tank bioreactors utilising knockouts of components of the flagella assembly system. The standard medium Hv-YPC was supplemented to reach a higher cell density. Without protein expression, cell dry weight reaches 10 g L . Two halophilic alcohol dehydrogenases were expressed under the control of the tryptophanase promoter p.tna with 16.8 and 3.2 mg g , respectively, at a maximum cell dry weight of 6.5 g L . Protein expression was induced by the addition of L-tryptophan. Investigation of various expression strategies leads to an optimised two-step induction protocol introducing 6 mM L-tryptophan at an OD of 0.4 followed by incubation for 16 h and a second induction step with 3 mM L-tryptophan followed by a final incubation time of 4 h. Compared with the uncontrolled shaker-flask cultivations used until date, dry cell mass concentrations were improved by a factor of more than 5 and cell-specific enzyme activities showed an up to 28-fold increased yield of the heterologous proteins.

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Section: Discussionmentioning

confidence: 99%

Production of halophilic proteins using Haloferax volcanii H1895 in a stirred-tank bioreactor

Strillinger

Grötzinger

Allers

et al. 2015

Appl Microbiol Biotechnol

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“…et al, 1973). It is possible that one function of kidney ASPA involves scavenging of aspartate and acetate from the low levels of NAA in the circulation, which would be especially important when diet was poor (Wolfe, 2005). In this regard it is interesting to note that the NaDC3 dicarboxylate transporter has recently been localized to proximal kidney tubule cells (Bai et al, 2006), the same cell type in the kidney in which ASPA is present.…”

Section: Four Cell-type Model For Naa Synthesis Utilization Breakdomentioning

confidence: 99%

N-Acetylaspartate in the CNS: From neurodiagnostics to neurobiology

Moffett

Ross

Arun

et al. 2007

Progress in Neurobiology

1,208

1,126

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The brain is unique among organs in many respects, including its mechanisms of lipid synthesis and energy production. The nervous system-specific metabolite N-acetylaspartate (NAA), which is synthesized from aspartate and acetyl-coenzyme A in neurons, appears to be a key link in these distinct biochemical features of CNS metabolism. During early postnatal CNS development, the expression of lipogenic enzymes in oligodendrocytes, including the NAA-degrading enzyme aspartoacylase (ASPA), is increased along with increased NAA production in neurons. NAA is transported from neurons to the cytoplasm of oligodendrocytes, where ASPA cleaves the acetate moiety for use in fatty acid and steroid synthesis. The fatty acids and steroids produced then go on to be used as building blocks for myelin lipid synthesis. Mutations in the gene for ASPA result in the fatal leukodystrophy Canavan disease, for which there is currently no effective treatment. Once postnatal myelination is completed, NAA may continue to be involved in myelin lipid turnover in adults, but it also appears to adopt other roles, including a bioenergetic role in neuronal mitochondria. NAA and ATP metabolism appear to be linked indirectly, whereby acetylation of aspartate may facilitate its removal from neuronal mitochondria, thus favoring conversion of glutamate to alpha ketoglutarate which can enter the tricarboxylic acid cycle for energy production. In its role as a mechanism for enhancing mitochondrial energy production from glutamate, NAA is in a key position to act as a magnetic resonance spectroscopy marker for neuronal health, viability and number. Evidence suggests that NAA is a direct precursor for the enzymatic synthesis of the neuron specific dipeptide N-acetylaspartylglutamate, the most concentrated neuropeptide in the human brain. Other proposed roles for NAA include neuronal osmoregulation and axon-glial signaling. We propose that NAA may also be involved in brain nitrogen balance. Further research will be required to more fully understand the biochemical functions served by NAA in CNS development and activity, and additional functions are likely to be discovered.

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“…The enzyme has a strong affinity for acetate (Km of 200µM), which allows it to function at low acetate concentrations, but it is inhibited by glucose [66,67]. On the other hand, the reversible ackA-pta pathway can assimilate acetate only at high acetate concentrations [15]. The overexpression of acs in E. coli resulted in a significant reduction in acetate formation during glucose metabolism.…”

Section: Pep Carboxylase (Ppc) and Pep Carboxykinase (Pck)mentioning

confidence: 99%

“…For more detailed information about why, when and how bacterial cells excrete acetate, see reference [15].…”

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confidence: 99%

Minimizing acetate formation in E. coli fermentations

Mey

Maeseneire

Soetaert

et al. 2007

J Ind Microbiol Biotechnol

199

144

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Escherichia coli remains the best established production organisms in industrial biotechnology. However, during aerobic fermentation runs at high growth rates, considerable amounts of acetate are accumulated as by-product. This by-product has negative effects on growth and protein production. Over the last 20 years, substantial research efforts have been spent to reduce acetate accumulation during aerobic growth of E. coli on glucose. From the onset it was clear that this quest should not be a simple nor uncomplicated one. Simple deletion of the acetate pathway, reduced the acetate accumulation, but instead other by-products were formed. This minireview gives a clear outline of these research efforts and the outcome of them, including bioprocess level approaches and genetic approaches. Recently, the latter seems to have some promising results

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The Acetate Switch

Cited by 1,066 publications

References 493 publications

Production of halophilic proteins using Haloferax volcanii H1895 in a stirred-tank bioreactor

Production of halophilic proteins using Haloferax volcanii H1895 in a stirred-tank bioreactor

N-Acetylaspartate in the CNS: From neurodiagnostics to neurobiology

Minimizing acetate formation in E. coli fermentations

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