Hydrogen sulfide (H2S), which is generated mainly by cystathionine γ-lyase (CSE) in the cardiovascular system, plays a pivotal role in a wide range of physiological and pathological processes. However, the regulatory mechanism of the CSE/H2S system is poorly understood. Herein, we show that oxidation induces the disulfide bond formation between Cys252 and Cys255 in the CXXC motif, thus stimulating the H2S-producing activity of CSE. The activity of oxidized CSE is approximately 2.5 fold greater than that of the reduced enzyme. Molecular dynamics and molecular docking suggest that the disulfide bond formation induces the conformational change in the active site of CSE and consequently increases the affinity of the enzyme for the substrate L-cysteine. Mass spectrometry and mutagenesis studies further established that the residue Cys255 is crucial for oxidation sensing. Oxidative stress-mediated sulfenylation of Cys255 leads to a sulfenic acid intermediate that spontaneously forms an intramolecular disulfide bond with the vicinal thiol group of Cys252. Moreover, we demonstrate that exogenous hydrogen peroxide (H2O2) and endogenous H2O2 triggered by vascular endothelial growth factor (VEGF) promote cellular H2S production through the enhancement of CSE activity under oxidative stress conditions. By contrast, incubation with H2O2 or VEGF did not significantly enhance cellular H2S production in the presence of PEG-catalase, an enzymatic cell-permeable H2O2 scavenger with high H2O2 specificity. Taken together, we report a new posttranslational modification of CSE that provides a molecular mechanism for H2O2/H2S crosstalk in cells under oxidative stress.
Keywords: cystathionine γ-lyase; hydrogen peroxide; hydrogen sulfide; oxidative stress; sulfenic acid modification.