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.

Guanya Jia

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