Mapping the Pro-Peptide of the Schistosoma mansoni Cathepsin B1 Drug Target: Modulation of Inhibition by Heparin and Design of Mimetic Inhibitors
Abstract
Blood flukes of the genus Schistosoma cause the disease schistosomiasis that infects over 200 million people worldwide. Schistosoma mansoni cathepsin B1 (SmCB1) is a gut-associated protease that digests host blood proteins as source of nutrients.
Enzymatic activity of the SmCB1 zymogen is prevented by the pro-peptide that sterically blocks the active site until activation of the zymogen to the mature enzyme. We investigated the structure-inhibition relationships of how the SmCB1 pro-peptide interacts with the enzyme core using a SmCB1 zymogen model and pro-peptide-derived synthetic fragments.
Two regions were identified within the pro-peptide that govern its inhibitory interaction with the enzyme core: an 'active site region' and a unique 'heparin-binding region' that requires heparin. Using the active site region as a template and a docking model of SmCB1, we designed a series of inhibitors mimicking the pro-peptide structure.