Biomaterial Database

Inactivation of prostaglandin H synthase and prostacyclin synthase by phenylbutazone. Requirement for peroxidative metabolism. 1985

G A Reed, and I O Griffin, and T E Eling

Phenylbutazone (PB), a nonsteroidal anti-inflammatory drug, is an efficient reducing cofactor for the peroxidase activity of prostaglandin H synthase (PHS). Most reducing cofactors for the peroxidase protect PHS and prostacyclin synthase from inactivation by hydroperoxides. PB, however, does not protect these enzymes, but rather augments their hydroperoxide-dependent inactivation. Using ram seminal vesicle microsomes as a source of PHS and prostacyclin synthase, we have examined the interaction of PB and exogenous hydroperoxides. Chromatographic analysis of the metabolism of 14C-labeled arachidonic acid in this system revealed that PB-dependent inactivation of PHS is markedly increased in the presence of 100 microM H2O2. This inactivation is a linear function of PB concentration between 10 and 250 microM, with a half-maximal effect in this range at about 100 microM PB. Prostacyclin synthase is even more sensitive to inactivation by the combined PB and H2O2 treatment, with a corresponding half-maximal effect at PB concentrations near 25 microM. This PB- and H2O2-dependent inactivation is demonstrable whether PGH2 is generated in situ from arachidonic acid or is added exogenously, supporting a direct effect of the treatment on prostacyclin synthase. As PB undergoes peroxide-dependent co-oxygenation catalyzed by PHS, we propose that it is an oxygenated derivative of PB, rather than the parent compound, which is responsible for the inactivation of PHS and prostacyclin synthase. Nafazatrom, a competitive inhibitor of PB co-oxygenation, blocks the effects of the PB and H2O2 treatment, supporting our proposal.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008054	Lipid Peroxides	Peroxides produced in the presence of a free radical by the oxidation of unsaturated fatty acids in the cell in the presence of molecular oxygen. The formation of lipid peroxides results in the destruction of the original lipid leading to the loss of integrity of the membranes. They therefore cause a variety of toxic effects in vivo and their formation is considered a pathological process in biological systems. Their formation can be inhibited by antioxidants, such as vitamin E, structural separation or low oxygen tension.	Fatty Acid Hydroperoxide,Lipid Peroxide,Lipoperoxide,Fatty Acid Hydroperoxides,Lipid Hydroperoxide,Lipoperoxides,Acid Hydroperoxide, Fatty,Acid Hydroperoxides, Fatty,Hydroperoxide, Fatty Acid,Hydroperoxide, Lipid,Hydroperoxides, Fatty Acid,Peroxide, Lipid,Peroxides, Lipid
D008297	Male		Males
D008861	Microsomes	Artifactual vesicles formed from the endoplasmic reticulum when cells are disrupted. They are isolated by differential centrifugation and are composed of three structural features: rough vesicles, smooth vesicles, and ribosomes. Numerous enzyme activities are associated with the microsomal fraction. (Glick, Glossary of Biochemistry and Molecular Biology, 1990; from Rieger et al., Glossary of Genetics: Classical and Molecular, 5th ed)	Microsome
D010545	Peroxides	A group of compounds that contain a bivalent O-O group, i.e., the oxygen atoms are univalent. They can either be inorganic or organic in nature. Such compounds release atomic (nascent) oxygen readily. Thus they are strong oxidizing agents and fire hazards when in contact with combustible materials, especially under high-temperature conditions. The chief industrial uses of peroxides are as oxidizing agents, bleaching agents, and initiators of polymerization. (From Hawley's Condensed Chemical Dictionary, 11th ed)	Peroxide
D010653	Phenylbutazone	A butyl-diphenyl-pyrazolidinedione that has anti-inflammatory, antipyretic, and analgesic activities. It has been used in ANKYLOSING SPONDYLITIS; RHEUMATOID ARTHRITIS; and REACTIVE ARTHRITIS.	Diphenylbutazone,Fenilbutazon,Butacote,Butadion,Butadione,Butapirazol,Butapyrazole,Butazolidin
D011453	Prostaglandins	A group of compounds derived from unsaturated 20-carbon fatty acids, primarily arachidonic acid, via the cyclooxygenase pathway. They are extremely potent mediators of a diverse group of physiological processes.	Prostaglandin,Prostanoid,Prostanoids
D011464	Epoprostenol	A prostaglandin that is a powerful vasodilator and inhibits platelet aggregation. It is biosynthesized enzymatically from PROSTAGLANDIN ENDOPEROXIDES in human vascular tissue. The sodium salt has been also used to treat primary pulmonary hypertension (HYPERTENSION, PULMONARY).	Prostacyclin,Prostaglandin I2,Epoprostanol,Epoprostenol Sodium,Epoprostenol Sodium Salt, (5Z,9alpha,11alpha,13E,15S)-Isomer,Flolan,Prostaglandin I(2),Veletri
D011720	Pyrazoles	Azoles of two nitrogens at the 1,2 positions, next to each other, in contrast with IMIDAZOLES in which they are at the 1,3 positions.
D003577	Cytochrome P-450 Enzyme System	A superfamily of hundreds of closely related HEMEPROTEINS found throughout the phylogenetic spectrum, from animals, plants, fungi, to bacteria. They include numerous complex monooxygenases (MIXED FUNCTION OXYGENASES). In animals, these P-450 enzymes serve two major functions: (1) biosynthesis of steroids, fatty acids, and bile acids; (2) metabolism of endogenous and a wide variety of exogenous substrates, such as toxins and drugs (BIOTRANSFORMATION). They are classified, according to their sequence similarities rather than functions, into CYP gene families (>40% homology) and subfamilies (>59% homology). For example, enzymes from the CYP1, CYP2, and CYP3 gene families are responsible for most drug metabolism.	Cytochrome P-450,Cytochrome P-450 Enzyme,Cytochrome P-450-Dependent Monooxygenase,P-450 Enzyme,P450 Enzyme,CYP450 Family,CYP450 Superfamily,Cytochrome P-450 Enzymes,Cytochrome P-450 Families,Cytochrome P-450 Monooxygenase,Cytochrome P-450 Oxygenase,Cytochrome P-450 Superfamily,Cytochrome P450,Cytochrome P450 Superfamily,Cytochrome p450 Families,P-450 Enzymes,P450 Enzymes,Cytochrome P 450,Cytochrome P 450 Dependent Monooxygenase,Cytochrome P 450 Enzyme,Cytochrome P 450 Enzyme System,Cytochrome P 450 Enzymes,Cytochrome P 450 Families,Cytochrome P 450 Monooxygenase,Cytochrome P 450 Oxygenase,Cytochrome P 450 Superfamily,Enzyme, Cytochrome P-450,Enzyme, P-450,Enzyme, P450,Enzymes, Cytochrome P-450,Enzymes, P-450,Enzymes, P450,Monooxygenase, Cytochrome P-450,Monooxygenase, Cytochrome P-450-Dependent,P 450 Enzyme,P 450 Enzymes,P-450 Enzyme, Cytochrome,P-450 Enzymes, Cytochrome,Superfamily, CYP450,Superfamily, Cytochrome P-450,Superfamily, Cytochrome P450