Importantly, this work shows that fusion of a HaloTag to PKA results in a substantial decrease in activity. Nonetheless, it remains viable as an immobilized enzyme. Having established this benchmark, future studies could focus on further optimizing the activity of Halo-PKA fusions through linker optimization studies . This work will be of utility to those who wish to study phosphoproteomics in cell lysates without the potentially complicating presence of the kinase. In addition, this immobilized kinase could be incorporated into a flow reactor system for the generation of recombinant phosphoproteins and has readily imagined applications in the characterization of novel kinase inhibitors and substrates. Finally, this work may provide a general roadmap for the immobilization of numerous kinases using HaloTag technology. One could envision application of a library of immobilized kinases that, when coupled with proteomics approaches, could rapidly tease out novel phosphorylation sites, protein interaction, and cellular signaling pathways. In our lab, investigations into these applications and others are currently underway.