Assay of adenosine 3',5'-cyclic monophosphate-dependent protein kinase activity by quantitative fast atom bombardment mass spectrometry.

Cyclic AMP-dependent protein kinase is conventionally assayed by measuring the incorporation of radiolabeled phosphate into a histone substrate. Here the assay of the protein kinase is carried out by the positive-ion fast atom bombardment mass spectrometric analysis of the enzyme incubation mixture after the reaction has been terminated. The data obtained are in good agreement with those obtained from the conventional radiometric assay of the same kinase preparation. The inherent advantage of this mass spectrometric assay is the capacity for multiple component monitoring; in addition to the kinase activity, the ability of the enzyme to bind cyclic nucleotides, together with integral ATPase and phosphodiesterase activity, can also be estimated from the same spectra.