title: A colorimetric assay method for 3beta-hydroxy-delta5-steroid dehydrogenase.
abstract: 3beta-Hydroxy-Delta5-steroid dehydrogenase is an important enzyme of steroid hormone biosynthesis present in steroidogenic tissues like adrenal, testis, and ovary of vertebrates. The enzyme is assayed mainly by radiochemical substrates. Spectrophotometric assay is not adequately sensitive to detect the enzyme activity since it is often present in low levels. We have developed a simple colorimetric assay based on formazan formation due to the reduction of the tetrazolium salt. The reaction mixture containing the substrate, pregnenolone or dehydroepiandrosterone, NAD and iodonitrotetrazolium in 0.1 M Tris-HCl buffer (pH 7.8), and the enzyme extract is incubated for 1 h at 37 degrees C. Absorbance at 490 nm is read in a spectrophotometer. The enzyme activity was linear with time and protein concentration. The assay works well with adrenal tissue extract, whereas in the case of testis, Leydig cell preparation may be required. We have assayed the enzyme activity in the adrenal of rat, mouse, and gerbil. The method is two- to threefold more sensitive than the spectrophotometric assay.
authors.affiliation: Department of Food Protectants and Infestation Control, Central Food Technological Research Institute, Mysore, 570013, India.
authors.forename: T
authors.initials: T
authors.lastname: Shivanandappa
authors.forename: S
authors.initials: S
authors.lastname: Venkatesh
mesh_terms: D000311:Adrenal Glands / Q000201:enzymology; D000818:Animals; D003124:Colorimetry / Q000379:methods*; D003687:Dehydroepiandrosterone / Q000378:metabolism; D004795:Enzyme Stability; D005260:Female; D005849:Gerbillinae; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008297:Male; D051379:Mice; D009243:NAD / Q000032:analysis / Q000378:metabolism; D011284:Pregnenolone / Q000378:metabolism; D011375:Progesterone Reductase / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012680:Sensitivity and Specificity; D013053:Spectrophotometry; D013737:Testis / Q000201:enzymology; D013778:Tetrazolium Salts / Q000032:analysis / Q000378:metabolism
chemical_list: D013778:Tetrazolium Salts; D009243:NAD; C013574:iodonitrotetrazolium; D003687:Dehydroepiandrosterone; D011284:Pregnenolone; D011375:Progesterone Reductase