Tyrosyl radicals and their role in hydroperoxide-dependent activation and inactivation of prostaglandin endoperoxide synthase

Tyrosyl radicals were characterized and their role in hydroperoxide-dependent regulation of prostaglandin endoperoxide (PGH) synthase were determined. A tyrosyl radical is formed during incubation of PGH synthase 1 with arachidonate or peroxide. No strong evidence for the role of this radical in cyclooxygenase catalysis was found. However, it is proposed that the radical is associated with suicide inactivation of the peroxidase activity of PGH synthase 1.