Exploring the steroidogenic activity of glutathione transferases across species

• Main Author: Lindström, Helena
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Stockholms universitet, Institutionen för biokemi och biofysik 2020
• Subjects: Glutathione transferase; steroidogenesis; GST A3-3; testis; androstenedione; pregnenedione; equine; steroidogenesis inhibition; Drosophila GSTE14; Biochemistry and Molecular Biology; Biokemi och molekylärbiologi; Canis lupus
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-179443

Glutathione transferases (GSTs) comprise a superfamily of enzymes prominently involved in detoxication. However, some GSTs have developed alternative functions. Thus, a member of the Alpha class GSTs in tissues of Homo sapiens (humans), Sus scrofa (pigs) and ruminants is involved in biosynthesis of steroid hormones, catalyzing a double-bond isomerization reaction as the last step of synthesis of Δ4-pregnene-3,20-dione (progesterone) and the obligatory step in the synthesis of the last precursor of testosterone, Δ4-androstenene-3,17-dione. Steroids regulate several vital aspects of life such as for example glucose homeostasis, inflammation, immunosuppression, blood pressure, reproduction and pregnancy. The human GST A3-3 was the most efficient steroid double-bond isomerase known so far in mammals. Our work extends discoveries of GSTs that act in the steroidogenic pathways in large mammals to Equus ferus caballus (horse). The kinetic profile of EcaGST A3-3 reveals a catalytic efficiency higher than that of the human enzyme making EcaGST A3-3 the most efficient steroid double-bond isomerase known today in mammals. In contrast to the rodents, Equus ferus caballus shares the steroidogenic pathway with Homo sapiens, which makes it a more suitable model for human steroidogenesis than the murine one. Inhibition of EcaGST A3-3 might help treat endocrine disorders. We screened a library of 1040 FDA-approved compounds for novel inhibitors of EcaGST A3-3 and made a further characterization of the most potent inhibitors. To extend the search for steroidogenic GSTs to other mammals, we probed the degree of GST A3-3 amino acid sequence conservation in Homo sapiens, Equus ferus caballus, Canis lupus familiaris (dog), Capra hircus (goat) and Monodelphis domestica (gray short-tailed opossum). We generated expression vectors containing homologous DNA from these species to facilitate further evaluation of the activity of these GSTs in mammals. We continued to expand the research to insects by investigating the steroidogenic ...