Synthesis and Evaluation of Multisubstrate Inhibitors of an Oncogene-Encoded Tyrosine-Specific Protein Kinase.

The synthesis and testing of potential multisubstrate inhibitors of tyrosine-specific protein kinases are described. One of the substrates, ATP, was mimicked by the known kinase inhibitor 5′-[4-(fluorosulfonyl)benzoyl]adenosine, which was covalently linked via the sulfonyl moiety to tyrosine mimics. The resulting multisubstrate inhibitors were tested for their ability to inhibit the transfer of phosphate from ATP to a protein acceptor by p^60v-abl the tyrosine kinase encoded by the transforming gene (v-abl) of the Abelson murine leukemia virus (A-MuLV). Although the series of inhibitors displayed moderately potent activity (IC₅₀ values as low as 19 μM), the absence of large effects produced by modification of the tyrosine mimic suggests that they do not behave as multisubstrate inhibitors but bind primarily through the adenosine moiety common to all the inhibitors. This interpretation is strengthened by the finding that the inhibitors lack specificity, inhibiting a serine kinase at comparable concentrations.