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Glutathione transferases (GSTs) comprise a superfamily of enzymes prominently involved in detoxication by making toxic electrophiles more polar and therefore more easily excretable. However some GSTs have developed alternative functions. Thus, a member of the Alpha class GSTs in pig and human tissues is involved in steroid hormone biosynthesis, catalyzing the obligatory double-bond isomerization of Δ 5 -androstene-3,17-dione to Δ 4 -androstene-3,17-dione and of Δ 5 -pregnene-3,20-dione to Δ 4 -pregnene-3,20-dione on the biosynthetic pathways to testosterone and progesterone. The human GST A3-3 is the most efficient steroid double-bond isomerase known so far in mammals. The current work extends discoveries of GST enzymes that act in the steroidogenic pathways in large mammals. The mRNA encoding the steroid isomerase GST A3-3 was cloned from testis of the horse ( Equus ferus caballus). The concentrations of GSTA3 mRNA were highest in hormone-producing organs such as ovary, testis and adrenal gland. EcaGST A3-3 produced in E. coli has been characterized and shown to have highly efficient steroid double-bond isomerase activity, exceeding its activities with conventional GST substrates. The enzyme now ranks as one of the most efficient steroid isomerases known in mammals and approaches the activity of the bacterial ketosteroid isomerase, one of the most efficient enzymes of all categories known today. The high efficiency and the tissue distribution of EcaGST A3-3 support the view that the enzyme plays a physiologically significant role in the biosynthesis of steroid hormones. [ABSTRACT FROM AUTHOR]

: ObjectiveTo determine if insulin or glucose action plays a role in adrenocortical steroidogenesis in the polycystic ovary syndrome (PCOS).: DesignProspective cohort study.: SettingAcademic medical center.: Patient(s)Nine reproductive-aged patients with PCOS and nine age-, race-, and body mass index–matched controls.: Main outcome measure(s)Insulin-modified frequently sampled intravenous glucose tolerance testing and an acute 60-minute ACTH-(1-24) stimulation test. From the glucose tolerance test, glucose and insulin were measured and the insulin sensitivity index, glucose effectiveness, and acute insulin response to glucose were determined. Dehydroepiandrosterone sulfate (DHEAS) basally and 17-hydroxypregnenolone, 17-hydroxyprogesterone, DHEA, androstenedione, and cortisol during ACTH testing at 0 and 60 minute (steroid0 and steroid60) were determined. The net change in steroid during the ACTH test was calculated.: Result(s)The insulin sensitivity index had limited correlation with adrenocortical variables in both groups. In patients with PCOS, glucose effectiveness was positively associated with DHEAS, cortisol0, cortisol60, change in cortisol, DHEA0, DHEA60, change in DHEA, 17-hydroxyprenenolone60, change in 17-hydroxypregnenolone, DHEA0, androstenedione0, 17-hydroxyprenenolone0, 17-hydroxyprogesterone0, 17-hydroxyprenenolone60, and 17-hydroxyprogesterone60.: Conclusion(s)Adrenocortical biosynthesis, basally and in response to ACTH, appears to be closely associated with glucose effectiveness in PCOS. A common factor determining both the effectiveness of glucose to control its own production or uptake and adrenocortical biosynthesis may be aberrant in PCOS. [Copyright &y& Elsevier]