Adenylate cyclase activity from Hirudo medicinalis segmental ganglia: modulation by calcium and calmodulin.

An adenylate cyclase activity stimulated by serotonin and calmodulin is present in the segmental ganglia of the leech Hirudo medicinalis. Removal of the endogenous calcium binding protein does not alter the responsiveness of the enzyme to serotonin. The calmodulin antagonist, trifluoperazine, drastically reduces the amine stimulatory effect on both intact and calmodulin-depleted membranes. We suggest that calmodulin-sensitive and serotonin-stimulated adenylate cyclase are, at least functionally, independent.