Two Types of Microsomal Prostaglandin E Synthase: Glutathione-Dependent and -Independent Prostaglandin E Synthases

doi:10.1006/bbrc.1997.6708

Biochemical and Biophysical Research Communications

Volume 235, Issue 1, 9 June 1997, Pages 148-152

https://doi.org/10.1006/bbrc.1997.6708 Get rights and content

Abstract

Prostaglandin (PG) E synthase was found to be widely distributed in the microsomal fractions of rat organs. Among them, an extremely high activity was seen in the deferent duct (112 nmol/min·mg) and other genital accessory organs (10-20 nmol/min·mg). In nongenital organs, the kidney had the highest activity (8 nmol/min·mg). Most of the PGE synthase activity in these organs required glutathione (GSH). In contrast, the enzyme activity in the heart, spleen, and uterine microsomes did not require GSH for its catalytic activity. In view of these data and those of other enzymatic parameters (Km values for PGH₂or pH optima), we suggest that two different types of PGE synthases, GSH-dependent and GSH-independent enzymes, are present in microsomal fractions of rat tissues.

References (19)

H. Matsumura et al.
Brain Res.
(1988)
N. Ogino et al.
J. Biol. Chem.
(1977)
P. Moonen et al.
Methods Enzymol.
(1982)
K. Watanabe et al.
J. Biol. Chem.
(1985)
O.H. Lowry et al.
J. Biol. Chem.
(1951)
R.W. Lerner et al.
Biochim. Biophys. Acta
(1992)
T. Shimizu et al.
J. Neurochem.
(1990)
A.J. Vander
Am. J. Physiol.
(1968)
A.S. Milton et al.
J. Physiol.
(1971)

There are more references available in the full text version of this article.

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Citation Excerpt :
However, as described below, studies of mPGES2 (EC 5.3.99.3) have produced contradictory results. mPGES2 was initially found in and purified from the microsomal fraction of bovine heart (2), and mRNAs encoding human and monkey homologs were subsequently identified (4, 5). Unlike mPGES1, mPGES2 was reported to be a GSH-independent enzyme (2, 4, 5).
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^☆: Abbreviations used: PG, prostaglandinGSH, glutathione; DTT, dithiothreitol;

¹: To whom correspondence should be addressed. Fax: 81-6-872-4818.

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Regular ArticleTwo Types of Microsomal Prostaglandin E Synthase: Glutathione-Dependent and -Independent Prostaglandin E Synthases☆

Abstract

Brain Res.

J. Biol. Chem.

Methods Enzymol.

J. Biol. Chem.

J. Biol. Chem.

Biochim. Biophys. Acta

J. Neurochem.

Am. J. Physiol.

J. Physiol.

Regular Article
Two Types of Microsomal Prostaglandin E Synthase: Glutathione-Dependent and -Independent Prostaglandin E Synthases☆