Abstract
1. 1. Several biochemical properties of adenylate cyclase were examined in particulate and detergent-solubilized preparations of gill tissue in Aplysia californica. 2. 2. Enzyme activity in a 38,000 g particulate fraction was stimulated 250-fold by NaF and 23-fold by guanyl-5′-yl-imidodiphosphate. Stimulation of activity by dopamine and 5-hydroxytryptamine displayed an absolute requirement for guanine nucleotide. 3. 3. Enzyme activity was supported by both Mg 2+ and Mn 2+, activity being 8-fold greater in the presence of saturating concentrations of the latter cation. 4. 4. Solubilization of the enzyme with nonionic detergents caused a loss in sensitivity to guanyl-5′-yl-imidodiphosphate while NaF stimulation was enhanced. 5. 5. In the presence of calmodulin, Ca 2+ augmented basal as well as dopamine- and serotonin-stimulated activity at concentrations below 10 μM; concentrations above this were inhibitory. 6. 6. The diterpene forskolin had no stimulatory action on either the membrane-bound or detergent-solubilized enzyme. 7. 7. The data show that neurohormone-sensitive adenylate cyclase in this invertebrate tissue resembles, in many respects, the enzyme from mammalian tissues.
Published Version
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