Figure 4.

Hydrolysis of cAMP isomers by purified tomato extracellular phosphodiesterase. Enzymatic hydrolysis of 2′:3′-cAMP (A–C) and 3′:5′-cAMP (D–F) was performed as described in “Materials and Methods.” Standard compounds (A and D), control incubations with heat-inactivated enzyme (B and E), and enzymatic digests for 30 min (C and F) were separated by reverse-phase HPLC on Butyl-Si 100. Peak identities: 1, 3′-AMP; 2, 2′-AMP; 3, 2′:3′-cAMP; 4, adenosine; 5, 5′-AMP; 6, 3′:5′-AMP.