Alpha amidating monooxygenase
Tissues capable of responding to endocrines have 2 properties in common: they posses a receptor having very high affinity for hormone, and the receptor is coupled to a process that regulates metabolism of the target cells.Receptors for most amino acid-derived hormones and all peptide hormones are located on the plasma membrane.The classic interactions between receptors, G-protein transducer, and membrane-localized adenylate cyclase are illustrated below using the pancreatic hormone glucagon as an example.When G-proteins bind to receptors, GTP exchanges with GDP bound to the α subunit of the G-protein.Other receptors are composed of multiple polypeptides.
Once a hormone is secreted by an endocrine tissue, it generally binds to a specific plasma protein carrier, with the complex being disseminated to distant tissues.
Subsequent to hormone binding, a signal is transduced to the interior of the cell, where second messengers and phosphorylated proteins generate appropriate metabolic responses.
The main second messengers are c AMP, Ca), and diacylglycerol (DAG).
Carriers for steroid and thyroid hormones allow these very hydrophobic substances to be present in the plasma at concentrations several hundred-fold greater than their solubility in water would permit.
Carriers for small, hydrophilic amino acid-derived hormones prevent their filtration through the renal glomerulus, greatly prolonging their circulating half-life.