The reaction of PGA1 with sulfhydryl groups; a component in the binding of A-type prostaglandins to proteins.

Prostaglandins of the A-type (PGAs) were found to react with cysteine or reduced glutathione to yield water-soluble adducts, an effect due to a reaction of the sulfhydryl group of cysteine with the unsaturated carbonyl function of these prostaglandins. The binding of tritiated PGA1 to the supernatant fraction of rabbit papilla homogenates reported by Attallah and Lee (4) appears to be related to this phenomenon since ethacrynic acid, a compound also highly reactive with the thiol group of cysteine, effectively competes with PGAs for the binding site in this soluble kidney preparation. Evidence is also presented to show that this binding of PGAs to the "acceptor' of the rabbit kidney is related to an interaction with a thiol group of 15-hydroxy prostaglandin dehydrogenase, the enzyme chiefly involved in the metabolism of prostaglandins.