Because of their critical role in modulating cellular cyclic nucleotide levels, phosphodiesterases (PDEs) are involved in many disease-related signaling pathways. The PDE family is large and diverse, with members having different tissue distribution, sub-cellular localizations, and substrate specificities. Because of these characteristics, the PDEs represent a broad group of potential drug targets. Described in the present unit are the assay development and validation procedures needed to establish a high-throughput screening system for these important enzymes. The assays provide a structured approach for determining the kinetic parameters of related enzyme families to facilitate the characterization of PDE inhibitors.
Bacterially expressed proteins used in NMR studies lack glycans, and proteins from other organisms are neither 15 N labeled nor glycosylated homogeneously. Here, we add two artificial glycans to uniformly 15 N labeled prion protein using a buffer system that evolves over a pH range to accommodate the conflicting pH requirements of the substrate and enzymes without the need to fine-tune buffer conditions. NMR and CD spectroscopy of the protein indicates that the glycans do not influence its fold.
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