Effect of 4'-chloro-5-methoxy-3-biphenylylacetic acid (DKA-9) on prostaglandin synthetase.

4'-Chloro-5-methoxy-3-biphenylylacetic acid (DKA-9) was evaluated for its ability to inhibit the conversion of arachidonic acid into prostaglandin E2 and the oxygen uptake on arachidonic acid by sheep seminal vesicle microsomes. DKA-9 inhibited equally the formation of prostaglandin E2 and oxygen uptake at 20 mumol/l or more in a concentration-dependent manner, which suggests a blockade of prostaglandin endoperoxide formation. DKA-9 did not promote time-dependent inactivation of the enzyme and inhibited the enzyme competitively with respect to substrate. Thus, it behaved as a reversible and competitive inhibitor.