ABSTRACT
Molecular mechanisms whereby H2S influences its targets have been of intriguing interest. In this work, L-lactic dehydrogenase ( L-LDH) was used as the protein target, and three kinds of H2S-donor reagents ( NaHS, Na2S, and polysulfide) were chosen. The interactions of these H2S-donor reagents with L-LDH were disclosed by molecular fluorescent assays for real-time monitoring of L-LDH activity. The results of the SDS-PAGE showed that H2S might not interact with L-LDH to form disulfide/trisulfide bonding. Circular dichroism spectra assays revealed that H2S reagents could be likely to react with cysteine thiols to yield sulfurated thiol (-SSH) derivatives in L-LDH, and sulfur-containing PS ( polysulfide) was a stronger protein S-sulfurating agent than the other two sulfides. Matrix assisted laser desorptionionization time-of-flight tandem mass spectrometry ( MALDI-TOF-MS/MS) study showed partial S-sulfuration of the active cysteine sites existed in L-LDH. In conclusion, H2S exerts its biological effects as a gasotransmitter through its reactions with cysteine thiols in proteins by S-sulfuration.