抄録
The enzyme which catalyzes the reduction of the cyclopentanone moiety of sodium 2-[4-(2-oxocyclopentylmethyl) phenyl] propionate dihydrate (loxoprofen sodium) was purified from rabbit liver cytosol to homogeneity as judged by polyacrylamide gel electrophoresis. The purified enzyme had a molecular weight of 33000, showed a preference for nicotineamide adenine dinucleotide phosphate as a cofactor and had an optimal pH of 6.2. The Km and Vmax values for the reduction of loxoprofen were 0.45mM and 0.81 μmol/min/mg protein, and the trans-alcohol was the main product. The reducing activity was inhibited by p-chloromercuribenzoate, N-ethylmaleimide and quercitrin. The enzyme efficiently catalyzed reduction of various aromatic aldehydes and ketones, cyclohexanones and 5α-3-ketosteroids. Cyclopentanone and its methylsubstituted derivatives were not reduced at all. However, 2-ethyl-and 2-n-propylcyclopentanone were reduced, and 2-benzylcyclopentanone was a good substrate, comparable to loxoprofen itself. These results strongly suggest that the loxoprofen reducing enzyme is probably identical with the aromatic aldehyde-ketone reductase (F3) of rabbit liver cytosol, identified as 3α-hydroxysteroid dehydrogenase by Sawada et al.
