title: [19-14C]androstenedione: a new substrate for assaying aromatase and studying its reaction mechanism.
abstract: [19-14C]Androstenedione has been prepared and utilized as a substrate for assaying microsomal human placental aromatase. Enzyme activity is determined by measuring the rate at which [14C]formate is produced by aromatization of this 14C-labeled steroid. Isotope ratio experiments using [19-14C]androstenedione and [1 beta-3H]androstenedione demonstrate that an apparent kinetic hydrogen isotope effect exists for the aromatization of the tritiated steroid with kH/kT approximately 1.09. Metabolic switching occurs to a minor extent (approximately 3%) during aromatization of [1 beta-3H]androstenedione, but not during the aromatization of [19-14C]androstenedione.
authors.affiliation: Department of Pharmacology, Washington University School of Medicine, St. Louis, MO 63110.
authors.forename: D F
authors.initials: DF
authors.lastname: Covey
authors.forename: P C
authors.initials: PC
authors.lastname: McMullan
authors.forename: L L
authors.initials: LL
authors.lastname: Wixler
authors.forename: M
authors.initials: M
authors.lastname: Cabell
mesh_terms: D000735:Androstenedione / Q000378:metabolism*; D001141:Aromatase / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D005561:Formates / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008861:Microsomes / Q000201:enzymology; D010920:Placenta / Q000201:enzymology; D012995:Solubility
chemical_list: D005561:Formates; C030544:formic acid; D000735:Androstenedione; D001141:Aromatase