Figure 10 Comparison of ELISA and HTRF methods for detection of cytokines. Both are capable of picogram levels of detection, but the HTRF assay is fewer steps.

Enzyme-mediated reactions that cleave, synthesize or modify compounds represent a significant group of targets for HTS. The HTRF assays can be constructed such that enzyme activity can be measured by the absence or presence of high signal. Protein tyrosine kinases play a critical role in the cellular signal transduction pathways, with significant implications for mechanisms of allograft rejection, allergic response, and autoimmune diseases. Hundreds of tyrosine kinases have been identified and many are still to be discovered through genomic research [17,18]. The following is an example of an HTRF tyrosine kinase assay.