Insulin Guanylate cyclase

Diacylglycerol, on the other hand, is lipid soluble and remains in the lipid bilayer of the membrane. There it can activate protein kinase C (PKC), a very important and widely distributed enzyme which serves many systems through phosphorylation, including neurotransmitters (acetylcholine, a,- and P-adrenoceptors, serotonin), peptide hormones (insulin, epidermal growth hormone, somatomedin), and various cellular functions (glycogen metabolism, muscle activity, structural proteins, etc.), and also interacts with guanylate cyclase. In addition to diacylglycerol, another normal membrane lipid, phos-phatidylserine, is needed for activation of PKC. The DG-IP3 limbs of the pathway usually proceed simultaneously. 

Two observations have given some clues as to the mode of transfer of information from membrane to cytoplasm. Insulin inhibits adenylate cyclase and thereby reduces the concentration of cyclic AMP in the cells, but stimulates guanylate cyclase and the synthesis of cyclic GMP, an inhibitor of adenylate cyclase. 

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