Episelection: novel Ki approximately nanomolar inhibitors of serine proteases selected by binding or chemistry on an enzyme surface.

A novel class of mechanism-based inhibitors of the serine proteases is developed using epitaxial selection. Tripeptide boronates esterified by an alcohol or alcohols at the boron retain the tight binding to trypsin-like enzymes associated with transition-state analogs and incorporate additional groups that can be utilized for selectivity between proteases. Formed by reaction of a series of alcohols with the inhibitor boronate oxygen(s), the most structurally compatible alcohol-derivatized inhibitors are either selected by binding to the enzyme (epitaxial selection) or assembled by epitaxial reaction on the enzyme surface. Mass spectrometry of the derivatized boronates and X-ray crystallography of the complexes identify the chemical structures and the three-dimensional interactions of inhibitors generated. This scheme also engineers novel, potent (Ki approximately 7 nM), and more specific inhibitors of individual serine proteases, by derivitizations of compounds obtained by epitaxial selection.