Quantitation of Nucleotidyl Cyclase and Cyclic Nucleotide-Sensitive Protein Kinase Activities by Fast-Atom Bombardment Mass Spectrometry: A Paradigm for Multiple Component Monitoring in Enzyme Incubations by Quantitative Mass Spectrometry

Abstract

AbstractTwo cyclic nucleotides, adenosine 3’,5’-cyclic monophosphate (cyclic AMP) and guanosine 3’,5’-cyclic monophosphate (cyclic GMP), are established components of biological signal transduction processes. Two sets of enzymes are identified as determinants of cyclic nucleotide activity in such regulatory processes; the nucleotidyl cyclases, which catalyse the synthesis of the cyclic nucleotide from the corresponding nucleoside triphosphate, and the cyclic nucleotide-responsive protein kinases, which are stimulated by the cyclic nucleotides to phosphorylate target proteins, thereby modifying their activity ( Scheme 1 ). This cyclic nucleotide signal is switched off by hydrolysis to a mononucleotide by phosphodiesterase. Whereas the cyclic AMP and cyclic GMP second messenger systems are major targets for pharmacologic manipulation, other cyclic nucleotides (cytidine-, inosine-, uridine-, and deoxythymidine-3’,5’-cyclic monophosphate) also occur naturally, together with enzymes capable of their synthesis and hydrolysis, but no precise physiological functions have yet been elucidated for these compounds. Scheme 1. KeywordsCyclic NucleotideCyclic MonophosphateRadiometric AssayCyclic Nucleotide SignalMike SpectrumThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.