Discovery of a novel enzyme mediating glucocorticoid catabolism in fish: 20beta-Hydroxysteroid dehydrogenase type 2

► Novel 20beta-hydroxysteroid dehydrogenase type 2 was discovered in zebrafish. ► The enzyme catalyzes the conversion of cortisone to 20beta-hydroxycortisone as identified by LC-MS/MS. ► Zebrafish 20beta-HSD type 2 shows the same expression pattern as 11beta-HSD type 2 that is known to oxidize cortisol to cortisone. ► In adult tissues, 20beta-HSD type 2 shows a ubiquitous expression pattern with some minor sex-specific differences. ► We propose that novel type 2 20beta-HSDs in teleost fish are important enzymes in cortisol catabolism.