Recombinant human microsomal prostaglandin E-2 synthase-1 (mPGES-1) was expressed in a baculovirus-Sf9 cell system. The mPGES-1 was solubilized from Sf9 cell membranes with diheptanoylphosphatidylcholine and purified in the presence of octylglucoside using hydroxyapatite column chromatography. The K-m values of the substrates PGH(2) and GSH were 14 muM and 0.75 mM, respectively, with the purified enzyme. The specific activity (4 mumol/min/mg) was increased 3-5-fold by non-ionic and zwitterionic detergents. Kinetic analysis showed that dodecylmaltoside increases V-max but does not affect the K-m values of either substrate. Several other thiol-containing compounds were tested as glutathione replacements, none of which yielded detectable enzyme activity. During enzyme catalysis, glutathione was not oxidized and therefore can be considered an enzyme cofactor. No glutathione transferase or peroxidase activity could be determined with a range of potential substrates. The results show that purified mPGES-1 has a specific activity similar to Cox-2, consistent with its postulated role in Cox-2 mediated PGE(2) formation. (C) 2002 Elsevier Science (USA). All rights reserved.