Document Detail

Stoichiometry and kinetics of the interaction of prostaglandin H synthase with anti-inflammatory agents.
MedLine Citation:
PMID:  3930499     Owner:  NLM     Status:  MEDLINE    
We have examined the kinetics, stoichiometry, and chemical nature of the interaction of three anti-inflammatory agents (indomethacin, flurbiprofen, and meclofenamic acid) with pure ovine prostaglandin H synthase. The kinetics of the interaction with the synthase for each of the three agents, monitored by the decrease in cyclooxygenase activity, was consistent with the model proposed by Rome and Lands (Rome, L.H., and Lands, W.E.M. (1975) Proc. Natl. Acad. Sci. U.S.A. 72, 4863-4865): a rapid and reversible initial binding, followed by a first-order decay of the synthase-inhibitor complex. A relatively stable form of the cyclooxygenase, which had 4-10% of the initial activity, was the eventual product of this decay process. The dissociation constants evaluated for the initial binding were 1.7 +/- 1.5 microM for indomethacin, 0.2 +/- 0.1 microM for flurbiprofen, and 0.08 +/- 0.06 microM for meclofenamic acid. The values of the first order rate constants for the subsequent decay process were 14.9 +/- 11.3 min-1 for indomethacin, 3.4 +/- 0.7 min-1 for meclofenamic acid, and 16.6 +/- 6.2 min-1 for flurbiprofen. In repeated titrations of the cyclooxygenase with the three agents, 1.3 +/- 0.3 mol of indomethacin, 1.2 +/- 0.1 mol of meclofenamic acid, and 1.2 +/- 0.1 mol of S-(+)-flurbiprofen/mol of synthase dimer were found to result in maximal inhibition of the enzyme. Racemic flurbiprofen required 2.4 +/- 0.3 mol/mol synthase dimer for full effect, and the R-(-)-isomer was not inhibitory. Inhibition of the cyclooxygenase activity by these agents thus appears to result from a stereospecific binding to only one of the subunits of the synthase. Intact indomethacin could be recovered quantitatively after prolonged incubation (in stoichiometric quantities) with the synthase had resulted in maximal inhibition of the cyclooxygenase activity. The time-dependent effect of indomethacin on the cyclooxygenase is thus likely to involve a conformational change in the synthase rather than a covalent interaction.
R J Kulmacz; W E Lands
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The Journal of biological chemistry     Volume:  260     ISSN:  0021-9258     ISO Abbreviation:  J. Biol. Chem.     Publication Date:  1985 Oct 
Date Detail:
Created Date:  1985-11-14     Completed Date:  1985-11-14     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  2985121R     Medline TA:  J Biol Chem     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  12572-8     Citation Subset:  IM    
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MeSH Terms
Anthranilic Acids / metabolism*
Arachidonic Acid
Arachidonic Acids / metabolism
Cyclooxygenase Inhibitors
Flurbiprofen / metabolism*,  pharmacology
Indomethacin / metabolism*,  pharmacology
Macromolecular Substances
Meclofenamic Acid / metabolism*,  pharmacology
Oxygen Consumption
Propionates / metabolism*
Prostaglandin-Endoperoxide Synthases / metabolism*
Protein Conformation / drug effects
Seminal Vesicles / enzymology
Grant Support
Reg. No./Substance:
0/Anthranilic Acids; 0/Arachidonic Acids; 0/Cyclooxygenase Inhibitors; 0/Macromolecular Substances; 0/Propionates; 506-32-1/Arachidonic Acid; 5104-49-4/Flurbiprofen; 53-86-1/Indomethacin; 644-62-2/Meclofenamic Acid; EC Synthases

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