Reaction: citrate = isocitrate (overall reaction)
(1a) citrate = cis-aconitate + H2O
(1b) cis-aconitate + H2O = isocitrate
For diagram click here and mechanism click here (see also glyoxylate cycle and citric acid cycle).
Glossary: isocitrate = (1R,2S)-1-hydroxypropane-1,2,3-tricarboxylate (previously known as threo-Ds-isocitrate)
cis-aconitate = (Z)-prop-1-ene-1,2,3-tricarboxylate
Other name(s): cis-aconitase; aconitase; AcnB; 2-methylaconitate hydratase; citrate(isocitrate) hydro-lyase
Systematic name: citrate(isocitrate) hydro-lyase (cis-aconitate-forming)
Comments: Besides interconverting citrate and cis-aconitate, it also interconverts cis-aconitate with isocitrate and, hence, interconverts citrate and isocitrate. The equilibrium mixture is 91% citrate, 6% isocitrate and 3% aconitate. cis-Aconitate is used to designate the isomer (Z)-prop-1-ene-1,2,3-tricarboxylate. An iron-sulfur protein, containing a [4Fe-4S] cluster to which the substrate binds.
Links to other databases: BRENDA, EXPASY, GTD, KEGG, Metacyc, PDB, CAS registry number: 9024-25-3
References:
1. Dickman, S.R. Aconitase. In: Boyer, P.D., Lardy, H. and Myrbäck, K (Eds.), The Enzymes, 2nd ed., vol. 5, Academic Press, New York, 1961, pp. 495-510.
2. Morrison, J.F. The purification of aconitase. Biochem. J. 56 (1954) 99-105. [PMID: 13126098]
3. Lauble, H., Kennedy, M.C., Beinert, H. and Stout, C.D. Crystal structures of aconitase with trans-aconitate and nitrocitrate bound. J. Mol. Biol. 237 (1994) 437-451. [PMID: 8151704]