All are second messengers EXCEPT?

Ans. D Guanylyl cyclaseRef: Gattong, 25"' ed. pg. 59* Guanylyl cyclase is an enzyme that catalyses the formation of cGMP.* cGMP is important for vision in both rods and cones.* Second messengers bring about short term changes by altering enzyme function, triggering exocytosis and can also lead to alteration of transcription of various genes* Examples of secondary messengers# cAMP: Produced by action of adenyl cyclase enzyme and stimulates protein kinase A which catalyses phosphorylation of proteins and altering there activity. For example cholera toxin increases cAMP levels whereas pertussis toxin inhibits it.# IP3: Inositol phosphate diffuses into endoplasmic reticulum and triggers calcium release.# DAG: Diacyglycerol works with IP3.