DEVELOPMENT OF A NEW METHOD FOR DETERMINATION OF 3β-HYDROXY STEROID DEHYDROGENASE ACTIVITY

3 beta-Hydroxy-Delta-5-steroid dehydrogenase is an important key anzyme of steroid hormone biosynthesis, which is involved in catalyzing the conversion of pregnenolone to progesterone in the biosynthesis of steroid sex hormones. This complex enzyme is the second enzyme in the steroid hormone biosynthesis pathway and it is identified as an autoantigenic target. In this study, a simple method is presented for the quantitative assay of 3β-Hydroxy steroid dehydrogenase activity in testis of rat. An excess of pregnenolone was incubated with several concentrations of whole testis homogenate. The reaction mixture containing the pregnenolone, NAD, isonitrotetrazolium in 0.15 M Tris-HCL buffer(PH=8) and the enzyme extract from testis of rat was incubated for 1.5 at 37˚c. Absorbance at 495 nm was read in a spectrophotometer. The results showed that 3-β-hydroxy steroid dehydrogenase activity was linear with time and protein concentration. The present method can easily be performed and is sensitive enough to assay 3-β-hydroxy steroid dehydrogenase activity in rat testis.