Short catalytic peptides with tunable activity: Cys confers functionality and adaptability

This study explores the catalytic potential of short peptides containing Cys, a potent nucleophile, able to hydrolyze a variety of ester substrates, including p-NPP and ATP, while enabling control and direction of catalytic activity through thiol oxidation. We identified Ac-CTLGLGSHCGG-Am (CG11), as a potential tunable catalyst capable of hydrolyzing ester and phosphoester substrates. We synthesized multiple analogues with varying sequence compositions and lengths and determined the effect of these changes on the catalytic efficiency. We showed that cyclization through disulfide bridge formation offered tunability and reversibility, while head-to-side chain cyclization conferred excellent resistance to proteases. Additionally, we demonstrated the ability of inactive cy-CG11 to undergo reduction and ring opening to its linear functional form in a physiological setting, specifically in the presence of elevated glutathione levels. These findings provide valuable insights for fine-tuning the characteristics of peptide-based catalysts and pave the way to their potential applicability in a biological context such as targeting glutathione disbalance and providing phosphatase activity.