title: New evidence of similarity between human and plant steroid metabolism: 5alpha-reductase activity in Solanum malacoxylon.
abstract: The physiological role of steroid hormones in humans is well known, and the metabolic pathway and mechanisms of action are almost completely elucidated. The role of plant steroid hormones, brassinosteroids, is less known, but an increasing amount of data on brassinosteroid biosynthesis is showing unexpected similarities between human and plant steroid metabolic pathways. Here we focus our attention on the enzyme 5alpha-reductase (5alphaR) for which a plant ortholog of the mammalian system, DET2, was recently described in Arabidopsis thaliana. We demonstrate that campestenone, the natural substrate of DET2, is reduced to 5alpha-campestanone by both human 5alphaR isozymes but with different affinities. Solanum malacoxylon, which is a calcinogenic plant very active in the biosynthesis of vitamin D-like molecules and sterols, was used to study 5alphaR activity. Leaves and calli were chosen as examples of differentiated and undifferentiated tissues, respectively. Two separate 5alphaR activities were found in calli and leaves of Solanum using campestenone as substrate. The use of progesterone allowed the detection of both activities in calli. Support for the existence of two 5alphaR isozymes in S. malacoxylon was provided by the differential actions of inhibitors of the human 5alphaR in calli and leaves. The evidence for the presence of two isozymes in different plant tissues extends the analogies between plant and mammalian steroid metabolic pathways.
authors.affiliation: Dipartimento di Fisiopatologia Clinica, Unità di Endocrinologia, Università di Firenze, I-50134 Firenze, Italy.
authors.forename: Fabiana
authors.initials: F
authors.lastname: Rosati
authors.forename: Giovanna
authors.initials: G
authors.lastname: Danza
authors.forename: Antonio
authors.initials: A
authors.lastname: Guarna
authors.forename: Nicoletta
authors.initials: N
authors.lastname: Cini
authors.forename: Milvia Luisa
authors.initials: ML
authors.lastname: Racchi
authors.forename: Mario
authors.initials: M
authors.lastname: Serio
mesh_terms: D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase / Q000235:genetics / Q000378:metabolism*; D058891:5-alpha Reductase Inhibitors; D000818:Animals; D001378:Azasteroids / Q000494:pharmacology; D016466:CHO Cells; D002783:Cholestenones / Q000378:metabolism; D006224:Cricetinae; D013196:Dihydrotestosterone / Q000031:analogs & derivatives* / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D018515:Plant Leaves / Q000201:enzymology; D018514:Plant Structures / Q000201:enzymology; D011374:Progesterone / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D032322:Solanum / Q000201:enzymology*; D013379:Substrate Specificity; D014162:Transfection
chemical_list: D058891:5-alpha Reductase Inhibitors; D001378:Azasteroids; D002783:Cholestenones; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D011994:Recombinant Proteins; D013196:Dihydrotestosterone; D011374:Progesterone; C031563:17-N,N-diethylcarbamoyl-4-methyl-4-azaandrostane-3-one; D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase