Peroxide-induced radical formation at TYR385 and TYR504 in human PGHS-1.

ABSTRACT: Prostaglandin H synthase isoforms 1 and -2 (PGHS-1 and -2) react with peroxide to form a radical on Tyr385 that initiates the cyclooxygenase catalysis. The tyrosyl radical EPR signals of PGHS-1 and -2 change over time and are altered by cyclooxygenase inhibitor binding. We characterized the tyrosyl radical dynamics using wild type human PGHS-1 (hPGHS-1) and its Y504F, Y385F, and Y385F/Y504F mutants to determine whether the radical EPR signal changes involve Tyr504 radical formation, Tyr385 radical phenyl ring rotation, or both. Reaction of hPGHS-1 with peroxide produced a wide singlet, whereas its Y504F mutant produced only a wide doublet signal, assigned to the Tyr385 radical. The cyclooxygenase specific activity and K(M) value for arachidonate of hPGHS-1 were not affected by the Y504F mu

SUBMITTER: Rogge CE 

PROVIDER: S-EPMC2697118 | biostudies-literature | 2009 Jun

REPOSITORIES: biostudies-literature