Document Detail

Peroxidative oxidation of leuco-dichlorofluorescein by prostaglandin H synthase in prostaglandin biosynthesis from polyunsaturated fatty acids.
MedLine Citation:
PMID:  8555252     Owner:  NLM     Status:  MEDLINE    
Prostaglandin H synthase can oxidize arachidonic acid with leuco-dichlorofluorescein as reducing cosubstrate. Addition of 0.5 mM phenol increases the oxidation of leuco-dichlorofluorescein to dichlorofluorescein 5-fold, probably by acting as a cyclic intermediate in the oxidation. Tetramethyl-p-phenylenediamine is also oxidized as cosubstrate. Its oxidation is not influenced by phenol. A stoichiometry of close to one mole of tetramethyl-p-phenylenediamine or leuco-dichlorofluorescein consumed per mole of arachidonic acid was found in the initial phase of the reaction. In the presence of phenol + leuco-dichlorofluorescein, the oxidation rate of arachidonic acid is about 40% lower than with phenol alone as cosubstrate. Since dichlorofluorescein has a molar extinction coefficient of 91 . 10(3) at 502 nm, the oxidation of less than 1 microM leuco-dichlorofluorescein can be detected spectrophotometrically. The rate of extinction change with leuco-dichlorofluorescein (at 502 nm) is about 4-fold more rapid than with tetramethyl-p-phenylenediamine (at 611 nm). With this spectrophotometric assay we have confirmed that arachidonic acid, linolenic acid, adrenic acid, gamma-linolenic acid, eicosapentaenoic acid, are substrates for prostaglandin H synthase with decreasing reaction rates in the mentioned order. The same order of reaction rates were found when oxygen consumption was measured. The assay also shows that docosahexaenoic acid is substrate for the enzyme. The reaction rate of the enzyme evidently is decreased both by a n-3 double bond and by deviation from a 20 carbon chain length of the fatty acid substrate.
L N Larsen; E Dahl; J Bremer
Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Biochimica et biophysica acta     Volume:  1299     ISSN:  0006-3002     ISO Abbreviation:  Biochim. Biophys. Acta     Publication Date:  1996 Jan 
Date Detail:
Created Date:  1996-02-26     Completed Date:  1996-02-26     Revised Date:  2005-11-17    
Medline Journal Info:
Nlm Unique ID:  0217513     Medline TA:  Biochim Biophys Acta     Country:  NETHERLANDS    
Other Details:
Languages:  eng     Pagination:  47-53     Citation Subset:  IM    
Institute of Medical Biochemistry, University of Oslo, Norway.
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MeSH Terms
Cyclooxygenase Inhibitors / pharmacology
Fatty Acids, Unsaturated / metabolism*
Fluoresceins / chemistry*
Horseradish Peroxidase
Hydrogen Peroxide
Hydrogen-Ion Concentration
Indomethacin / pharmacology
Phenols / pharmacology
Prostaglandin-Endoperoxide Synthases / chemistry,  metabolism*
Prostaglandins / biosynthesis*
Serum Albumin, Bovine / pharmacology
Substrate Specificity
Reg. No./Substance:
0/Cyclooxygenase Inhibitors; 0/Fatty Acids, Unsaturated; 0/Fluoresceins; 0/Phenols; 0/Prostaglandins; 0/Serum Albumin, Bovine; 108-95-2/Phenol; 2044-85-1/diacetyldichlorofluorescein; 53-86-1/Indomethacin; 7722-84-1/Hydrogen Peroxide; EC 1.11.1.-/Horseradish Peroxidase; EC Synthases

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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