STRUCTURE AND KINETICS OF FORMATION OF CATECHOL COMPLEXES OF FERRIC SOYBEAN LIPOXYGENASE-1

Ferric soybean lipoxygenase forms stable complexes with 4-substituted catechols. The structure of the complex between the enzyme and 3,4-dih ydroxybenzonitrile has been studied by resonance Raman, electron param agnetic resonance, visible, and X-ray spectroscopies. It is a bidentat e iron-catecholate complex with at least one water ligand. The kinetic s of formation of complexes between lipoxygenase and 3,4-dihydroxybenz onitrile and 3,4-dihydroxyacetophenone have been studied by stopped-fl ow spectroscopy. The data are consistent with two kinetically distinct , reversible steps. The pH dependence of the first step suggests that the substrate for the reaction is the catechol monoanion. When these r esults are combined, plausible mechanisms for the complexation reactio n are suggested.