Cyclic nucleotide esterification: Relationship to phosphate ring geometry and growth regulation in synchronized human lymphocytes

Infrared spectra of neutral aqueous solutions of nucleoside 3′,5′-cyclic monophosphates indicate an increase in the antisymmetric phosphoryl stretching frequency to 1236 cm −1 from 1215 cm −1 in trimethylene cyclic phosphates. A further increase to 1242 cm −1 accompanies esterification of the 2′-ribose hydroxyl. The O 2′-esterified and 2′-deoxy cyclic nucleotides examined display both reduced kinase binding and altered phosphoryl stretching frequencies, suggesting that modification of the phosphate ring represents a common feature in decreased kinase activation. Reversible inhibition of mitosis in thymidine-synchronized human lymphocytes by 2 m m N 6, O 2′-dibutyryladenosine 3′,5′-cyclic monophosphate and N 6-monobutyryladenosine 3′,5′-cyclic monophosphate was observed. However, adenosine 3′,5′-cyclic monophosphate, O 2′-monobutyryladenosine 3′,5′-cyclic monophosphate, butyric acid, and ethyl butyrate had no effect on mitosis when present at 2 m m concentrations during S and G2. These results are consistent with hydrolysis of O 2′-monobutyryladenosine 3′,5′-cyclic monophosphate and adenosine 3′,5′-cyclic monophosphate by esterase and phosphodiesterase enzymes and suggest that modification of the N 6 amino group is necessary for the antimitotic activity of N 6, O 2′-dibutyryladenosine 3′, 5′-cyclic monophosphate.