Screening derivatized peptide libraries for tight binding inhibitors to carbonic anhydrase II by electrospray ionization-mass spectrometry

This paper describes the use of electrospray ionization-mass spectrometry (ESI-MS) to screen two libraries of soluble compounds to search for tight binding inhibitors for carbonic anhydrase II (EC 4.2.1.1). The two libraries, H₂NO₂SC₆H₄C(O)NH-AA₁-AA₂-C(O)NHCH₂CH₂CO₂H (1), where AA₁ and AA₂ are L-amino acids (library size: 289 compounds) or D-amino acids (256 compounds), were constructed by attaching tripeptides to the carboxyl group of 4-carboxybenzenesulfonamide. Screening of both libraries yielded, as the tightest binding inhibitor, compound 1 (AA, = AA₂ = L-Leu; binding constant K(b) = 1.4 x 10⁸ M^-1). The ability of ESI-MS to estimate simultaneously the relative binding affinities of a protein to soluble ligands in a library, if general, should be useful in drug development.