To the left is shown the 3D structure of NADP-dependent isocitrate dehydrogenase IDH from Escherichia coli, complexed with isocitrate dehydrogenase, Ca2+ and NADP.
Isocitrate dehydrogenase is one of the enzymes involved in the Kreb's cycle. It catalyses the oxidation of isocitrate to alpha-ketoglutarate, with NADP acting as a coenzyme (in the case of E.coli -- eukaryotes have a NAD dependent form of the enzyme as well). The reaction is facilitated by a divalent metallic cofactor (Mg2+, Mn2+, etc.)
SRS entry for IDH