Purification and characterization of membrane-bound prostaglandin E synthase from bovine heart

Prostaglandin (PG) E synthase was solubilized with 6 mM sodium deoxycholate from the microsomal fraction of bovine hearts. The enzyme was purified by about 800-fold to apparent homogeneity. The specific activity of the purified enzyme was about 830 mU/mg of protein, and the Km value for PGH2 was 24 μM. The molecular weight of the enzyme was about 31 000 on SDS-polyacrylamide gel electrophoresis and was about 60 000 by gel filtration. The enzyme was separated from glutathione (GSH) S-transferase by DEAE-Toyopearl column chromatography, and did not exhibit any GSH S-transferase activity towards four different substrates. The purified enzyme was active in the absence of GSH, but it was activated by various SH-reducing reagents including dithiothreitol, GSH, or β-mercaptoethanol. This is the first reported purification of membrane-bound PGE synthase to apparent homogeneity.