Guanylate kinase is essential for recycling GMP and cGMP.  It catalyzes the ATP-dependent phosphorylation of GMP into GDP.  Guanylate kinase is an attractive antibacterial target.  The guanylate

GMP   +   ATP       =           GDP    +    ADP

kinase assay is based on measurement of ADP generated from the kinase reaction.  The assay is fluorescence-based and can be carried out using regular black 96-well or 384-well plates or cuvettes.  

E. coli Guanylate Kinase Assay Kit Plus (Catalog number: GMK100KE)

E. coli Guanylate Kinase Assay Kit Plus-500 (Catalog number: GMK500KE)

S. pneumoniae Guanylate kinase Assay Kit Plus-500 (GMK500KN)