Investigating Active Site Binding of Ligands to High and Low Activity Carbonic Anhydrase Enzymes Using Native Mass Spectrometry.

Carbonic anhydrases (CAs) are a family of enzymes that play an important pH regulatory role in health and disease. While different CA isozymes have a high degree of structural similarity, they have variable enzymatic activity, with CA III being the least active and having less than 1% of the activity of CA II, the most active. Furthermore, ligand binding studies for CA III are limited, and a resulting lack of chemical probes impedes understanding of this CA isozyme in comparison to other CA family members where studies are abundant. Therefore, we employed native mass spectrometry (nMS), also known as intact mass spectrometry, to assess ligand binding to CA II and CA III and discovered two novel compounds that for the first time display strong binding to CA III. We present a new data visualization and quantification tool developed to display native mass spectra as an intuitive stacked heat map representation for rapidly interpreting the results of ligand-protein binding from nMS screening.