Influence of an 18-hydroxyl group on the interaction of oestrogens and hydroxysteroid oxidoreductases.
1. Partially purified 17beta-hydroxy steroid-NAD(+) oxidoreductases, prepared from Pseudomonas testosteroni (EC 1.1.1.51), human term placenta (EC 1.1.1.62) and the cytoplasmic fraction of rat liver (EC 1.1.1.-) were tested for their ability to catalyse the oxidoreduction of 18-hydroxyoestradiol-17beta and 18-hydroxyoestrone. The products of incubation were identified by chromatographic procedures and by mass spectrometry. 2. The Pseudomonas enzyme catalysed both the oxidation of 18-hydroxyoestradiol-17beta and the reduction of 18-hydroxyoestrone; in contrast, the placental and rat liver enzymes only catalysed the reduction of 18-hydroxyoestrone. 3. These results were confirmed, by using a spectrophotometric assay; equimolar quantities of oestradiol-17beta and 18-hydroxyoestradiol-17beta were oxidized at approximately the same rate by the microbial enzyme. 4. These findings suggest that 18-hydroxyoestradiol-17beta may be a normal oestrogen metabolite. 5. The differences in ability of the mammalian and microbial enzymes to metabolize 18-hydroxylated oestrogens is explained on the basis of recognition sites with different geometrical dimensions, characteristic of the placental (Descomps & Crastes de Paulet, 1969) and the microbial steroid enzymes (Fosset & Crastes de Paulet, 1967).
D000818:Animals; D001665:Binding Sites; D002250:Carbon Radioisotopes; D002849:Chromatography, Gas; D002850:Chromatography, Gel; D002855:Chromatography, Thin Layer; D003593:Cytoplasm / Q000201:enzymology; D004967:Estrogens / Q000378:metabolism*; D005260:Female; D006801:Humans; D006913:Hydroxysteroid Dehydrogenases / Q000378:metabolism*; D007700:Kinetics; D008099:Liver / Q000166:cytology / Q000201:enzymology; D008297:Male; D013058:Mass Spectrometry; D008954:Models, Biological; D008968:Molecular Conformation; D010920:Placenta / Q000201:enzymology; D011247:Pregnancy; D011485:Protein Binding; D011549:Pseudomonas / Q000201:enzymology; D051381:Rats; D013056:Spectrophotometry, Ultraviolet; D013329:Structure-Activity Relationship
D002250:Carbon Radioisotopes; D004967:Estrogens; D006913:Hydroxysteroid Dehydrogenases