Enzymatic regulation of ligands

Enzymes are clearly important for the biosynthesis of steroid hormones and in their conversion to inactive metabolites for excretion. More recently, in addition to these roles in tissues of origin and disposal, it has become clear that enzymes also have important roles--for steroid and thyroid hormones, and for vitamin A derivatives--in both tissues of passage and target tissues. These actions may be reversible or essentially irreversible, and may activate or inactivate signals, thus affecting both the intensity and specificity of hormone action. In this paper, the involvement of 11 beta-hydroxysteroid dehydrogenase in adrenal steroid action is presented as a case study.