Allosteric control of ?II-tryptase by a redox active disulfide bond.

ABSTRACT: The S1A serine proteases function in many key biological processes such as development, immunity, and blood coagulation. S1A proteases contain a highly conserved disulfide bond (Cys(191)-Cys(220) in chymotrypsin numbering) that links two ?-loop structures that define the rim of the active site pocket. Mast cell ?II-tryptase is a S1A protease that is associated with pathological inflammation. In this study, we have found that the conserved disulfide bond (Cys(220)-Cys(248) in ?II-tryptase) exists in oxidized and reduced states in the enzyme stored and secreted by mast cells. The disulfide bond has a standard redox potential of -301 mV and is stoichiometrically reduced by the inflammatory mediator, thioredoxin, with a rate constant of 350 m(-1) s(-1). The oxidized and reduced enzymes have different substrate specificity and catalytic efficiency for hydrolysis of both small and macromolecular substrates. These observations indicate that ?II-tryptase activity is post-translationally regulated by an allosteric disulfide bond. It is likely that other S1A serine proteases are similarly regulated.

SUBMITTER: Cook KM 

PROVIDER: S-EPMC3843103 | biostudies-literature | 2013 Nov

REPOSITORIES: biostudies-literature