Alpha amidating monooxygenase
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).
Adenylate cyclase then converts ATP to c AMP and the subsequent increases in c AMP lead to activation of c AMP-dependent protein kinase (PKA) as shown in the Figure below.
GPCRs also couple to G-protein activation of phospholipase C-β (PLCβ).
Insulin-like growth factor-I (IGF-I), which behaves as an endocrine, paracrine, and autocrine, provides a prime example of this difficulty.
The G-GTP complex binds adenylate cyclase, activating the enzyme.
The activation of adenylate cyclase leads to c AMP production in the cytosol and to the activation of PKA, followed by regulatory phosphorylation of numerous enzymes. For more information on G-proteins and GPCRs visit the Signal Transduction page.
In addition, systemic feedback mechanisms have evolved to regulate the production of endocrine hormones.
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.
Hormones are normally present in the plasma and interstitial tissue at concentrations in the range of 10M.