Aconitase is an enzyme that catalyses the stereo-specific

Stereochemistry

Stereochemistry, a subdiscipline of chemistry, involves the study of the relative spatial arrangement of atoms within molecules. An important branch of stereochemistry is the study of chiral molecules....

 isomerization of citrate

Citrate

A citrate can refer either to the conjugate base of citric acid, , or to the esters of citric acid. An example of the former, a salt is trisodium citrate; an ester is triethyl citrate.-Other citric acid ions:...

 to isocitrate via cis-aconitate in the tricarboxylic acid cycle, a non-redox

Redox

Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....

-active process.
In contrast with the majority of iron-sulfur protein

Iron-sulfur protein

Iron-sulfur proteins are proteins characterized by the presence of iron-sulfur clusters containing sulfide-linked di-, tri-, and tetrairon centers in variable oxidation states...

s that function as electron carriers, the iron-sulfur cluster

Iron-sulfur cluster

For biological Fe-S clusters, see iron-sulfur proteins.Iron-sulfur clusters are ensembles of iron and sulfide centres. Fe-S clusters are most often discussed in the context of the biological role for iron-sulfur proteins. Many Fe-S clusters are known in the area of organometallic chemistry and as...

 of aconitase reacts directly with an enzyme substrate. Aconitase has an active [Fe₄S₄]²⁺ cluster, which may convert to an inactive [Fe₃S₄]⁺ form.