SYNTHESIS OF PROSTAGLANDIN F ETHANOLAMIDE BY PGF SYNTHASE AND IDENTIFICATION OF BIMATOPROST AS A POTENT PGFS INHIBITOR

Abstract

Abstract: : Purpose: The conversion of anandamide to PG–ethanolamides (prostamides) by COX–2 has been extensively reported. The intent of these studies was to determine whether PG–ethanolalmides were substrates for PGF synthase (PGFS), with the formation of the PGF–ethanolamides. Methods: Human purified PGFS was expressed in E. Coli HB101. Enzymatic activity was measured by a new method, liquid chromatographic–electrospray ionization mass spectrometry (LC/ESI/MS). This is a non–radioisotopic technique that allows all products to be simultaneously detected. Results: PGFS catalysed the reduction of prostamide D₂ to 9α, 11ß–prostamide F₂. The K_cat/K_m value for prostamide D₂ was 361 min^–1 M^–1, which is similar to that of PGH₂, which is 368 min^–1 M^–1). The effects of various compounds on the 3 PGFS activities (PGD₂ 11–ketoreductase, Prostamide D₂ 11–ketoreductase, and PGH₂ 9,11–endoperoxide reductase) were examined. Interestingly, bimatoprost inhibited all three enzyme activities with IC₅₀ values of 5, 60, and 6 x 10^–6 M respectively, in a non–competitive manner. Conclusions: (i) the products formed from anandamide by COX–2 occur with similar diversity to those produced from arachidonic acid. (ii) Bimatoprost is a PGFS inhibitor.

Keywords: eicosanoids • enzymes/enzyme inhibitors • pharmacology