Aconitase A catalytic domain. This is the major form of the TCA cycle enzyme aconitate hydratase, also known as aconitase and citrate hydrolyase. It includes bacterial and archaeal aconitase A, and the eukaryotic cytosolic form of aconitase. This group also includes sequences that have been shown to act as an iron-responsive element (IRE) binding protein in animals and may have the same role in other eukaryotes.