Inhibitory mechanism of tyrosinase-induced browning in Agaricus bisporus by garlic-derived H2S: Nucleophilic attack leading to catalytic-cu flexible loop collapse and thiol-persulfidation.

Tyrosinase (TY) drives melanin accumulation and enzymatic browning in produce. This study explored the inhibition mechanism of garlic-derived H2S on TY and its feasibility in preventing Agaricus bisporus browning. Garlic sulfides, including diallyl trisulfide (DATS), diallyl disulfide (DADS), and diallylthiosulfinate (Allicin), all inhibited TY activity via reduced glutathione (GSH)-induced H2S release, with DATS exhibiting the strongest effect due to its high Sn0 content. H2S bound TY at a single site, disrupted hydrogen bonds and hydrophobic interactions, reducing α-helix content, weakening van der Waals forces, inducing Cys83 persulfidation, destabilized the flexible loop, and increased the CuA-CuB distance. The "Nucleophilic attack leading to flexible loop collapse and persulfidation" mechanism enriches the biochemical theory of H2S as enzyme inhibitors. Additionally, garlic-derived H2S effectively reduced browning, malondialdehyde levels, PPO/POD activity, and volatile flavor deterioration in Agaricus bisporus homogenate, providing a novel strategy for natural TY inhibitors and fresh-produce preservation.