PURIFICATION AND CHARACTERIZATION OF A 15-KETOPROSTAGLANDIN DELTA-13-REDUCTASE FROM BOVINE LUNG

15-Ketoprostaglandin δ13-reductase from bovine lung has been purified using affinity chromatography to apparent homogeneity, as judged from polyacrylamide gel electrophoresis with and without sodium dodecyl sulphate. Valine was identified as the N-terminal amino acid, and the isoelectric point was estimated at pH 7.8. Molecular weights of 56 000 and 39 500 were found by the use of gel filtration and SDS-polyacrylamide gel electrophoresis, respectively. The enzyme was found to be specific for the 15-keto group, thus 15-ketoprostaglandin E1 (apparent Km = 10 μm) is a substrate, in contrast to prostaglandin E1. The enzyme was active with both NADH (apparent Km = 88-94 μM) and NADH (apparent Km = 5-9 μM) as coenzyme, but the V max with NADH was more than twice that obtained with NADPH. The enzyme did not catalyze the reversed reaction: 13,14-dihydro-15-keto-prostaglandin E1 to 15-ketoprostaglandin E1. The turnover number of the enzyme was determined to be either 60 or 42 min-1. The low value of the turnover number is compensated by a high concentration (96.4 mU/g tissue) of the enzyme in lung tissue, resulting in a high metabolic capacity. Thus, 15-ketoprostaglandin δ13-reductase together with 15-hydroxyprostaglandin dehydrogenase ensures an irreversible catabolism of prostaglandins. © 1979.