A major concern in attempts to relate the structure of soluble ribonucleic acid with biological specificity is whether an entire molecule of the acid is needed for biological function. Specific monophosphatases and esonucleases offer a tool with which to approach this question. Hydrolysis of S-RNA’ with venom phosphodiesterase (1) destroys the amino acid-accepting ability of S-RNAs (2, 3), pres...

1. We have tested the hypothesis that insulin might decrease the levels of cyclic AMP (CAMP) in rat epididymal adipose tissue by stimulating the activity of a CAMP phosphodiesterase. 2. Dibutyryl cyclic AMP (DBcAMP) was comparable to CAMP as a substrate for CAMP phosphodiesterase of adipose tissue; the hydrolysis of both cyclic nucleotides was inhibited by theophylline. 3. DBcAMP, but not CAMP,...