Prostaglandin 9-ketoreductase from pig and human kidney: purification, properties and identity with human carbonyl reductase.

Prostaglandin 9-ketoreductase has been purified to apparent homogeneity from pig and human kidney with an overall yield of 6%. The enzyme has a molecular mass of 34 kDa, it is present as an active monomer in diluted solution and contains approx. 2 equivalents Zn++/mole enzyme. It is stereoselective for the pro(S) hydrogen of NADPH and reduces the prostaglandin 9-keto group to yield 90% prostaglandin F2 alpha and 8% of the beta-form. An extensive study of the catalytic properties was carried out, which leads to the conclusion that the enzyme function in vivo is unlikely a catalysis of oxidation/reduction at the prostaglandin 9-position. Five peptides from the pig kidney enzyme were sequenced and compared with the sequence of carbonyl reductase from human placenta. The identity is > 90% and this, together with the immunological cross-reactivity with human brain carbonyl reductase, most strongly suggests that prostaglandin 9-ketoreductase and carbonyl reductase are the same enzyme.