Rapid inactivation of prostaglandin endoperoxide synthases by N-(carboxyalkyl)maleimides.
N-(Carboxyalkyl)maleimides were synthesized as potential inhibitors of prostaglandin endoperoxide synthase (PGHS). Inactivation of the cyclooxygenase and peroxidase activities of PGHS occurred in a biphasic manner with extremely rapid inactivation followed by slow, time-dependent inactivation. The carboxylic acid moiety was required for rapid inactivation. Optimal inhibition was observed with N-(carboxyheptyl)maleimide, which inhibited the cyclooxygenase activity of ovine PGHS-1 with an IC50 of 0.1 microM and the peroxidase activity with an IC50 of 3 microM. Inactivation of peroxidase activity was not prevented by pretreating the enzyme with the cyclooxygenase inhibitor indomethacin. N-(Carboxyheptyl)-succinimide inhibited neither enzyme activity, suggesting that covalent modification is critical for rapid as well as time-dependent inactivation. Shortening or increasing the alkyl chain by one methylene unit drastically reduced inhibitory potency. N-(Carboxyalkyl)maleimides also instantaneously inactivated the inducible form of PGHS (PGHS-2) from mouse and human sources but with higher IC50's (4.5 and 14 microM, respectively). N-(Carboxyheptyl)maleimide is the most potent covalent inactivator of PGHS yet described with an inhibitory potency 3-5 orders of magnitude greater than aspirin.
A. B. Hancock, Jr., Memorial Laboratory for Cancer Research, Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232.
A S
AS
Kalgutkar
L J
LJ
Marnett
D000818:Animals; D016861:Cyclooxygenase Inhibitors / Q000737:chemistry*; D006801:Humans; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D008301:Maleimides / Q000737:chemistry / Q000494:pharmacology*; D051379:Mice; D011451:Prostaglandin-Endoperoxide Synthases / Q000737:chemistry*; D012756:Sheep; D013329:Structure-Activity Relationship
D016861:Cyclooxygenase Inhibitors; D008301:Maleimides; D011451:Prostaglandin-Endoperoxide Synthases; D007213:Indomethacin