Iron and aconitase activity

Gawron, Oscar; Waheed, Abdul; Glaid, Andrew J.; Jaklitsch, A

doi:10.1042/bj1390709

Cited by 39 publications

(27 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Activation of macrophages by IFN-y and LPS alters aconitase activity and IRE binding activity reciprocally In preliminary assays, we observed that cytosolic aconitase was fully active in extracts and did not require activation by incubation with Fe2+ and a thiol as required for its mitochondrial counterpart (Gawron et al, 1974). In a first series of experiments, the effect of IFN-,y and LPS, which are potent macrophage activators, was analysed.…”

Section: Resultsmentioning

confidence: 91%

Biosynthesis of nitric oxide activates iron regulatory factor in macrophages.

et al. 1993

View full text Add to dashboard Cite

Biosynthesis of nitric oxide (NO) from L‐arginine modulates activity of iron‐dependent enzymes, including mitochondrial acontiase, an [Fe‐S] protein. We examined the effect of NO on the activity of iron regulatory factor (IRF), a cytoplasmic protein which modulates both ferritin mRNA translation and transferrin receptor mRNA stability by binding to specific mRNA sequences called iron responsive elements (IREs). Murine macrophages were activated with interferon‐gamma and lipopolysaccharide to induce NO synthase activity and cultured in the presence or absence of NG‐substituted analogues of L‐arginine which served as selective inhibitors of NO synthesis. Measurement of the nitrite concentration in the culture medium was taken as an index of NO production. Mitochondria‐free cytosols were then prepared and aconitase activity as well as IRE binding activity and induction of IRE binding activity were correlated and depended on NO synthesis after IFN‐gamma and/or LPS stimulation. Authentic NO gas as well as the NO‐generating compound 3‐morpholinosydnonimine (SIN‐1) also conversely modulated aconitase and IRE binding activities of purified recombinant IRF. These results provide evidence that endogenously produced NO may modulate the post‐transcriptional regulation of genes involved in iron homeostasis and support the hypothesis that the [Fe‐S] cluster of IRF mediates iron‐dependent regulation.

show abstract

Section: Resultsmentioning

confidence: 91%

Biosynthesis of nitric oxide activates iron regulatory factor in macrophages.

et al. 1993

View full text Add to dashboard Cite

show abstract

“…Two flavoenzymes were shown to catalyze HF elimina- , even though it is considered to work by the same protonjhydride oxidation mechanism [30] as butyryl-CoA dehydrogenase [31]. It may well be that HF loss from fluoropropionyl-CoA is assisted by the carbonyl function of the thioester, a facilitation which clearly would not work in monofluorosuccinate and Msubstituted-/Muoro-carboxylic acids.…”

Section: Mechanistic Consequences Of the Effect Of Halogen Replacemenmentioning

confidence: 99%

Baker's yeast flavocytochrome b₂

Urban

Lederer

1984

European Journal of Biochemistry

View full text Add to dashboard Cite

It has been shown that reduced flavocytochrome b2 not only catalyzes reduction of bromopyruvate [P. Urban, P.M. Alliel and F. Eur. J. Biochem. 134,275 -2811 but also transforms it into pyruvate in a reductive elimination process. The dehydrohalogenation reaction also takes place when oxidized enzyme acts on bromolactate, but the reaction is more difficult to observe under these conditions because of its low efficiency compared to the normal oxidative process. The maximal rates of pyruvate production from bromopyruvate and chloropyruvate differ by a factor of less than 10, whereas elimination from fluoropyruvate cannot be detected. These results support a mechanism in which the dehydrohalogenation reaction takes place from a carbanion intermediate of the normal reductive-oxidative pathway.The mechanism of flavoprotein-catalyzed dehydrogenation reactions has been under active investigation in recent years. For oxidations of the type H -4 -Z H + ,C = Z, the so-called carbanion mechanism is generally accepted, although not proven (for reviews, see [I, 21). The dehydrohalo genation of 3-chlorosubstrates by some dehydrogenases/oxidases constituted one of the first pieces of evidence in favour of the carbanion mechanism. The D-and L-amino-acid oxidases were shown to catalyze the non-oxidative transformation of 3-chloroalanine and 2-amino-3-chlorobutyrate to pyruvate and 2-ketobutyrate respectively [3, 41. Similarly, lactate oxidase from Mycohucterium smegrnatis catalyzed the non-oxidative transformation of 3-chlorolactate to pyruvate [S]. On the basis of available evidence, it was suggested that an a-carbanion was an intermediate common to the pathways of the normal oxidative reaction and of the non-oxidative halide ion elimination [3,5]. Other interpretations, however, could not be ignored underlined that the kinetic evidence did not rule out elimination from an Ered. P complex; in that case its occurrence did not allow deductions concerning the redox mechanism. Subsequently, in rapidreaction studies under anaerobic conditions, lactate oxidase appeared to be first reduced by 3-chlorolactate, then reoxidized before reaching the steady state [9]. Furthermore, 3-chlorolactate was not dehydrohalogenated by baker's yeast flavocytochrome b2 (a dehydrogenase/electron transferase) and kidney L-hydroxyacid oxidase, even though it was normally oxidized by the two enzymes [lo, 1 I]. In those two cases it was proposed that carbanion processing might be much faster than chloride ion elimination. It is, however, clear that one of the important pieces of evidence in favour of a carbanion mechanism was missing for those enzymes.In this paper we describe experiments which demonstrate that flavocytochrome b2 can actually catalyze the dehydro- halogenation of some 3-halogenosubstrates. The elimination is much easier to observe under the transhydrogenation conditions recently described by us [12], starting from reduced enzyme and a halogenopyruvate, than during the normal reaction between oxidized enzyme and the corresponding 3-halogen...

show abstract

“…However, the possibility that it is also involved in the catalytic mechanism cannot be discounted. Gawron & Jones (1977) have suggested that a ferrous ion might undergo successive oxidation and reduction in polarizing the double bond of cis-aconitic acid prior to hydration. The ironsulfur cluster of aconitase might conceivably participate in catalysis by a similar mechanism.…”

Section: Resultsmentioning

confidence: 98%

“…Tricarballylate, which is a competitive inhibitor of the enzyme (Gawron & Jones, 1977), was used to stabilize the enzyme. Spectroscopic analyses of aconitase were done at 4.0 mg/mL in this same buffer.…”

Section: Methodsmentioning

confidence: 99%

Analysis of the iron-sulfur cluster of aconitase by natural and magnetic circular dichroism

1981

Self Cite

View full text Add to dashboard Cite

We have examined the iron-sulfur cluster of aconitase, a high-potential iron-sulfur protein, by absorption, circular dichroism (CD), and magnetic circular dichroism (MCD) spectroscopy. The MCD spectrum of unactivated aconitase, which is presumably oxidized, is similar to those of reduced two iron-two sulfide ferredoxins but distinct from the MCD of known four iron-four sulfide proteins. The magnitude of the natural CD of unactivated aconitase also suggests the absence of four iron-four sulfur clusters. Reduction of the enzyme with dithionite and activation with the cysteine-ascorbate-ferrous ion activation mixture generate spectra which are significantly different from those of any iron-sulfur protein seen to date. We interpret these results as indicating that aconitase does not contain a four iron-four sulfur cluster generally thought to be characteristic of high-potential iron-sulfur proteins. It could contain a two iron-two sulfur center or some other center such as a cyclic three iron-three sulfur center.

show abstract

Iron and aconitase activity

Cited by 39 publications

References 15 publications

Biosynthesis of nitric oxide activates iron regulatory factor in macrophages.

Biosynthesis of nitric oxide activates iron regulatory factor in macrophages.

Baker's yeast flavocytochrome b₂

Analysis of the iron-sulfur cluster of aconitase by natural and magnetic circular dichroism

Contact Info

Product

Resources

About

Iron and aconitase activity

Cited by 39 publications

References 15 publications

Biosynthesis of nitric oxide activates iron regulatory factor in macrophages.

Biosynthesis of nitric oxide activates iron regulatory factor in macrophages.

Baker's yeast flavocytochrome b2

Analysis of the iron-sulfur cluster of aconitase by natural and magnetic circular dichroism

Contact Info

Product

Resources

About

Baker's yeast flavocytochrome b₂