The activation of aconitase by ferrous ions and reducing agents

Morrison, J. F.

doi:10.1042/bj0580685

Cited by 103 publications

(37 citation statements)

References 7 publications

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“…The in.wnce of iron on aconitase activity Some workers have reported that ferrous ions activate purified preparations of aconitase from mammalian tissues (Dickman & Cloutier, 1950Morrison, 1954). By using Morrison's methods in the present work it was found that, when precipitated with ammonium sulphate and dialysed, the partially purified aconitase of Aspergillus niger could be activated 4-fold by adding iron and cysteine.…”

Section: J M La Nauzementioning

confidence: 55%

Aconitase and Isocitric Dehydrogenases of Aspergillus niger in Relation to Citric Acid Production

Nauze

1966

Journal of General Microbiology

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SUMMARYAconitase and NAD-and NADP-linked isocitric dehydrogenases were examined in two strains of Aspergillus niger. The mutant strain 72-44 produced higher yields of citric acid on the culture medium used than did the parent strain 7 2 4 . After growth for 22 hr on a medium in which citric acid did not accumulate, the amounts of each enzyme in the parent strain were approximately the same as those in the mutant strain. The enzymes were also found, though in lower amounts, throughout the incubation period of 8 days in both strains grown on a medium in which citric acid accumulated. A 20-fold increase in the concentration of iron in this medium doubled the activity of aconitase in extracts from the mutant strain, though citric acid accumulation was only decreased by 25 %. The addition of monofluoroacetate to the culture medium was toxic to the mould and did not stimulate citric acid yields. It is suggested that during the incubation, some recycling of citric acid may take place. The difference in citric acid yields from the parent and mutant strains was not accounted for on the basis of the degrees of aconitase or isocitric dehydrogenase activity.

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Section: J M La Nauzementioning

confidence: 55%

Aconitase and Isocitric Dehydrogenases of Aspergillus niger in Relation to Citric Acid Production

Nauze

1966

Journal of General Microbiology

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“…Aconitase activity was measured as described previously (30). Briefly, 100 M trisodium citrate, 0.7 units of isocitrate dehydrogenase, and 270 M NADP ϩ were added to cleared cell lysates in assay buffer (20 mM Tris-HCl, pH 7.4).…”

Section: Methodsmentioning

confidence: 99%

The Influence of Iron on Pseudomonas aeruginosa Physiology

Oglesby-Sherrouse

Farrow

Lee

et al. 2008

Journal of Biological Chemistry

186

152

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In iron-replete environments, the Pseudomonas aeruginosa Fur (ferric uptake regulator) protein represses expression of two small regulatory RNAs encoded by prrF1 and prrF2. Here we describe the effects of iron and PrrF regulation on P. aeruginosa physiology. We show that PrrF represses genes encoding enzymes for the degradation of anthranilate (i.e. antABC), a precursor of the Pseudomonas quinolone signal (PQS). Under ironlimiting conditions, PQS production was greatly decreased in a ⌬prrF1,2 mutant as compared with wild type. The addition of anthranilate to the growth medium restored PQS production to the ⌬prrF1,2 mutant, indicating that its defect in PQS production is a consequence of anthranilate degradation. PA2511 was shown to encode an anthranilate-dependent activator of the ant genes and was subsequently renamed antR. AntR was not required for regulation of antA by PrrF but was required for optimal iron activation of antA. Furthermore, iron was capable of activating both antA and antR in a ⌬prrF1,2 mutant, indicating the presence of two distinct yet overlapping pathways for iron activation of antA (AntR-dependent and PrrF-dependent). Additionally, several quorum-sensing regulators, including PqsR, influenced antA expression, demonstrating that regulation of anthranilate metabolism is intimately woven into the quorum-sensing network of P. aeruginosa. Overall, our data illustrate the extensive control that both iron regulation and quorum sensing exercise in basic cellular physiology, underlining how intermediary metabolism can affect the regulation of virulence factors in P. aeruginosa.Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen that causes serious infections in immuno-compromised individuals, such as burn victims, and in cystic fibrosis (CF) 2 patients. To cause disease, P. aeruginosa expresses several virulence factors that allow it to colonize and survive within its host, as well as a variety of systems that allow for the acquisition of nutrients required for metabolism and growth. P. aeruginosa must be able to coordinate the expression of each of these factors to successfully establish and maintain infection. For example, a shortage of iron availability leads to the increased expression of iron acquisition systems and decreased expression of pathways that rely on relatively large amounts of iron. Conversely, the potential for iron toxicity necessitates the tight regulation of iron acquisition in response to iron availability, a function mediated through the action of the ferric uptake regulator (Fur) protein. Under iron-replete conditions, the Fur protein becomes ferrated and binds to a 19-bp consensus sequence, called the Fur box, in the promoters of genes required for iron uptake, thereby preventing their transcription (1, 2). In P. aeruginosa, Fur directly or indirectly controls the expression of a large number of genes and operons involved in iron uptake, as well an assortment of virulence genes (3-6). Fur can also contribute to the increased expression of genes via the repressi...

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“…34 Briefly, 100 L extracts containing equal amounts of protein was added to 800 L of a solution containing 330 mM Tris-HCl, pH 7.4, 1.5 mM manganese sulfate, 0.6 mM NADP, and 1 U/mL isocitrate dehydrogenase. The reaction was started by adding 100 L of 20 mM sodium citrate, and production of NADPH was monitored by measuring the increase in absorbance at 340 nm.…”

Section: Aconitase (Ec 4213) Assaymentioning

confidence: 99%

Overexpression of mitochondrial ferritin causes cytosolic iron depletion and changes cellular iron homeostasis

Nie

Sheftel

Kim

et al. 2005

Blood

154

158

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Cytosolic ferritin sequesters and stores iron and, consequently, protects cells against iron-mediated free radical damage. However, the function of the newly discovered mitochondrial ferritin (MtFt) is unknown. To examine the role of MtFt in cellular iron metabolism, we established a cell line that stably overexpresses mouse MtFt under the control of a tetracycline-responsive promoter. The overexpression of MtFt caused a dose-dependent iron deficiency in the cytosol that was revealed by increased RNA-binding activity of iron regulatory proteins (IRPs) along with an increase in transferrin receptor levels and decrease in cytosolic ferritin. Consequently, the induction of MtFt resulted in a dramatic increase in cellular iron uptake from transferrin, most of which was incorporated into MtFt. The induction of MtFt caused a shift of iron from cytosolic ferritin to MtFt. In addition, iron inserted into MtFt was less available for chelation than that in cytosolic ferritin and the expression of MtFt was associated with decreased mitochondrial and cytosolic aconitase activities, the latter being consistent with the increase in IRPbinding activity. In conclusion, our results indicate that overexpression of MtFt causes a dramatic change in intracellular iron homeostasis and that shunting iron to MtFt likely limits its availability for active iron proteins. IntroductionFerritins are ubiquitous, highly conserved iron storage proteins that play a critical role in cellular and organismal iron homeostasis. In mammalian cells, cytosolic ferritin consists of 2 subunits, the H and L chains. Twenty-four subunits assemble to form a spherical shell that can contain up to 4500 atoms of iron in a mineral and compact form. 1,2 In ferritin shells, the H subunit has ferroxidase activity that converts soluble ferrous ions into inert ferric hydroxides. The L subunit lacks ferroxidase activity but is more efficient than the H subunit in inducing iron nucleation and mineralization within the shells. 3,4 Ferritin H and L chain mRNAs have identical ironresponsive elements (IREs) at their 5Ј-untranslated regions (UTRs) that bind to cytosolic iron regulatory proteins IRP1 and IRP2 by an iron-dependent mechanism. 2,5 When the level of iron in the so-called "labile iron pool" (LIP) is low, translation of ferritin mRNA is suppressed by the binding of IRPs to IREs, whereas iron supplementation up-regulates ferritin synthesis through the conversion of IRP1 to cytosolic aconitase and the degradation of IRP2. [5][6][7][8] Mitochondria have a key role in iron metabolism because heme and various iron-sulfur (Fe-S) cluster-containing proteins are synthesized in them. 9,10 The last step in heme biosynthesis, the insertion of Fe 2ϩ into protoporphyrin IX by ferrochelatase, occurs in the mitochondrial matrix. 9 Fe-S clusters are synthesized mainly, if not entirely, in mitochondria and are combined with mitochondrial apo-proteins to form mature proteins or are exported from mitochondria for use by cytosolic and nuclear proteins. 10 Mitochondrial iron level mu...

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The activation of aconitase by ferrous ions and reducing agents

Abstract: In all instances the reaction cis-aconitate-* citrate was studied. Citric acid was estimated by the method of Pucher, Sherman & Vickery (1936) as modified by Buffa & Peters (1949).

Cited by 103 publications

References 7 publications

Aconitase and Isocitric Dehydrogenases of Aspergillus niger in Relation to Citric Acid Production

Aconitase and Isocitric Dehydrogenases of Aspergillus niger in Relation to Citric Acid Production

The Influence of Iron on Pseudomonas aeruginosa Physiology

Overexpression of mitochondrial ferritin causes cytosolic iron depletion and changes cellular iron homeostasis

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