Enzymatic radioiodination of succinyl cyclic AMP tyrosine methyl ester by lactoperoxidase and radioimmunoassay for cyclic AMP.

A highly specific and simple radioimmunoassay for cyclic AMP with a sensitivity of 0.04 picomoles/tube has been developed according to the method of Steiner et al., using 125I-succinyl cyclic AMP tyrosine methyl ester as a tracer. The tracer with higher immunoactivities could be simply and constantly prepared by an enzymatic iodination procedure utilizing lactoperoxidase, radioactive iodide and hydrogen peroxide generated by glucose-glucose oxidase system, rather than by chloramine-T procedure.