11β-Hydroxysteroid dehydrogenase-type 2 evolved from an ancestral 17β-Hydroxysteroid dehydrogenase-type 2

► Proteins with clear sequence similarity to 17β-Hydroxysteroid dehydrogenase-type 2 evolved in sea urchin and acorn worm, two basal deuterostomes. ► Sea urchin contains a novel ancestral 17β-Hydroxysteroid dehydrogenase-type 2 that may have a non-catalytic function. ► 17β-Hydroxysteroid dehydrogenase-type 2 in acorn worm may have catalytic activity. ► Proteins with clear sequence similarity to 11β-Hydroxysteroid dehydrogenase-type 2 first appear in sharks.