Properties of an adenyl cyclase partially purified from frog erythrocytes

Abstract

A particulate adenyl cyclase has been purified 150–200 fold from the erythrocytes of adult Rana Pipiens. The enzyme catalyzed the synthesis of cyclic 3′,5′-AM 32P from α-labeled AT 32P in the presence of NaF, Mg 2+ or Mn 2+ and a sulfhydryl compound. Catecholamines stimulated enzymic activity in the absence of fluoride to the extent of 50–75% of that demonstrable in the presence of fluoride. The ability of different catecholamines to stimulate enzymic activity paralleled their potency as β-adrenergic compounds. Sensitivity to stimulation by catecholamines was a labile function preserved only by storage of the enzyme in liquid N 2. The purified adenyl cyclase fraction did not contain cyclic 3′,5′-nucleotide phosphodiesterase activity, exhibited optimal activity at pH 8.0, and was inhibited by Zn 2+ or Ca 2+. dATP was the only nucleoside triphosphate other than ATP which was able to serve as a substrate for the formation of a cyclic 3′,5′-nucleotide. Phase microscopy, density gradient centrifugation, enrichment for ATPase activity, and the content of sialic acid and lipid phosphorus all suggested that the particulate enzyme was a fragment of the cell membrane.