Aconitase

Aconitase (ACO) is an enzymatic domain that confers the ability to catalyse the equilibrium

citrate = aconitate + H₂O = isocitrate

This reaction is part of the citrate (TCA-, Krebs-)cycle.

In most organims, there is a cytosolic enzyme with an ACO domain (cAc), and in eukaryotes, a second copy of it was introduced with mitochondria (mAc). Plants developed even more copies in mitochondria.

spinqualitylabelsall models Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

A specialty of cAc is that in mammals it has developed a second function as inhibitor of those mRNA that carry an iron-regulatory element (IRE). Therefore, the cytosolic cAc is named IREBP for IRE-binding protein when this function is talked about. Only one of the two functions is active, depending on whether the (4Fe4S) cofactor is present in the molecule: it's essential for the ACO function. You can see, by looking at the morph, how much the enzyme structure differs between those two functions.

WeblinksWeblinks

• Molecule of the Month: Aconitase and Iron Regulatory Protein 1
• Aconitase at Wikipedia