Aconitase, Porcine Heart

Citrate (isocitrate) hydro-lyase (EC 4.2.1.3) \n\nAconitase (aconitate hydratase; EC 4.2.1.3), from pig heart, is an enzyme that catalyses the stereo-specific isomerization of citrate to isocitrate via cis-aconitate in the tricarboxylic acid cycle, a non-redox-active process. By contrast with the majority of iron-sulfur proteins that function as electron carriers, the iron-sulfur cluster of aconitase reacts directly with an enzyme substrate. Aconitase has an active [Fe4S4]2+ cluster, which may convert to an inactive [Fe3S4]+ form. Three cysteine (Cys) residues have been shown to be ligands of the [Fe4S4] centre. In the active state, the labile iron ion of the [Fe4S4] cluster is not coordinated by Cys but by water molecules.\n\nThe iron-responsive element binding protein (IRE-BP) and 3-isopropylmalate dehydratase (a-isopropylmalate isomerase; EC 4.2.1.33), an enzyme catalysing the second step in the biosynthesis of leucine, are known aconitase homologues. Iron regulatory elements (IREs) constitute a family of 28-nucleotide, non-coding, stem-loop structures that regulate iron storage, heme synthesis and iron uptake. They also participate in ribosome binding and control the mRNA turnover (degradation). The specific regulator protein, the IRE-BP, binds to IREs in both 5' and 3' regions, but only to RNA in the apo form, without the Fe-S cluster. Expression of IRE-BP in cultured cells has revealed that the protein functions either as an active aconitase, when cells are iron-replete, or as an active RNA-binding protein, when cells are iron-depleted. Mutant IRE-BPs, in which any or all of the three Cys residues involved in Fe-S formation are replaced by serine, have no aconitase activity, but retain RNA-binding properties.\n\nAconitase is inhibited by fluoroacetate, therefore fluoroacetate is poisonous. The iron sulfur cluster is highly sensitive to oxidation by superoxide[1].\n\nStandard: Aconitase-05\n\nSpecific Activity: (same/more than) 5u/mg protein (25 degrees C, pH 7.4)\n\nState: Highly purified enzyme in solution \nOne ml of solution contains the following \nProtein 1~30mg \nGlycerol 50% \npH 7.0

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SPECIFICATIONS

Catalog Number

A0660

Size

100U

Form

Supplied as 50% glycerol solution.

Purity

Highly Purified

References

1. Aconitase: sensitive target and measure of superoxide. Methods Enzymol, 2002. 349: p. 9-23.\n2. Beinert, H., Kennedy, M.C. and Stout, C.D. (1996). \"Aconitase as iron-sulfur protein, enzyme, and iron-regulatory protein\". Chem. Rev. 96: 2335