title: A dopamine sensitive adenylate cyclase in the salivary glands of Amblyomma americanum (L.).
abstract: 1. Enzyme activity, basal or dopamine-stimulated (10 microM), was linear with time to 25 min and with protein concentration to 0.8 mg protein/ml of final assay volume. Activity was maximal between pH 7.0 and 7.5. 2. Mg2+ maximally stimulated basal or dopamine-sensitive adenylate cyclase activity at about 4 mM. 3. Adenylate cyclase had a Km of 0.042 mM for ATP and maximum velocities for basal and dopamine-stimulated activity of 107 and 179 pmol cyclic AMP formed/mg protein per min, respectively. 4. Half-maximal stimulation of the enzyme occurred at about 4.2 x 10(-7) M dopamine with the threshold being less than 10(-9) M. Dopamine increased the Vmax but had no effect on the Km of ATP. 5. Eighty-five to 90% of the adenylate cyclase activity was found in the particulate fraction. 6. Calcium ion produced a marked inhibition of adenylate cyclase activity above 0.04 mM and half-maximal inhibition occurred near 0.1-0.2 mM.
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D004298:Dopamine / Q000378:metabolism*; D005260:Female; D005459:Fluorides / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000494:pharmacology; D008274:Magnesium / Q000494:pharmacology; D012469:Salivary Glands / Q000201:enzymology*; D013987:Ticks / Q000201:enzymology*
chemical_list: D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D000262:Adenylyl Cyclases; D008274:Magnesium; D005459:Fluorides; D002118:Calcium; D004298:Dopamine