Schematic representation of the three-dimensional structure of soybean lipoxygenase-1. The α-helices and β sheets are represented by cylinders and arrows, respectively. Domain I, the smaller of the two domains, is on the far left and consists of a single β barrel comprising the N-terminal 146 residues. Domain II is the larger domain comprising the C-terminal 693 residues. Domain II contains the iron, represented by the yellow ball, and the active site of the enzyme. (Illustration courtesy of Betty Gaffney, Florida State University.)