Persulfidation of Human Cystathionine γ-Lyase Inhibits Its Activity: A Negative Feedback Regulation Mechanism for H₂S Production

Cystathionine γ-lyase (CSE) is the second enzyme in the trans-sulfuration pathway that converts cystathionine to cysteine. It is also one of three major enzymes responsible for the biosynthesis of hydrogen sulfide (H₂S). CSE is believed to be the major source of endogenous H₂S in the cardiovascular system, and the CSE/H₂S system plays a crucial role in a variety of physiological and pathological processes. However, the regulatory mechanism of the CSE/H₂S system is less well understood, especially at the post-translational level. Here, we demonstrated that the persulfidation of CSE inhibits its activity by ~2-fold in vitro. The loss of this post-translational modification in the presence of dithiothreitol (DTT) results in a reversal of basal activity. Cys137 was identified as the site for persulfidation by combining mass spectrometry, mutagenesis, activity analysis and streptavidin–biotin pull-down assays. To test the physiological relevance of the persulfidation regulation of CSE, human aortic vascular smooth muscle cells (HA-VSMCs) were incubated with vascular endothelial growth factor (VEGF), which is known to enhance endogenous H₂S levels. Under these conditions, consistent with the change tendency of the cellular H₂S level, the CSE persulfidation levels increased transiently and then gradually decreased to the basal level. Collectively, our study revealed a negative feedback regulation mechanism of the CSE/H₂S system via the persulfidation of CSE and demonstrated the potential for maintaining cellular H₂S homeostasis under oxidative stress conditions, particularly in tissues where CSE is a major source of H₂S.