15-hydroxy-9-oxoprosta-11, 13-dienoic acid as the product of a prostaglandin isomerase.

The initial product of the interaction between prostaglandin A(1) and the prostaglandin isomerase of cat blood plasma has been isolated. By ultraviolet spectroscopy and mass spectrometry and from stability and chromatographic studies, the structure of the compound has been established as 15-hydroxy-9-oxoprosta-11,13-dienoic acid, an allylic isomer of prostaglandin A(1). The compound is unstable under mild alkaline conditions, isomerizing to prostaglandin B(1). The biological significance of the enzymatic isomerization of prostaglandin A(1) is discussed.