Ribbon diagram of rabbit 15-lipoxygenase. Domain I, on the upper left, is a single β-barrel comprising the N-terminal 11 amino acids. Domain II, the larger of the two domains, is the catalytic domain and is predominately α-helical. The green space filling structure in the middle of domain II represents the inhibitor RS75091 bound at the active site. The mammalian lipoxygenase contains 177 fewer amino acids and in general has a more compact structure compared to the soybean enzyme. (Illustration courtesy of S. Gilmor, University of California, San Francisco, and M. Browner, Roche Bioscience.)