Aged black garlic-derived S-allyl-L-cysteine serves as a dietary precursor for supersulfide production by cystathionine γ-lyase.

S-allyl-L-cysteine (SAC) is a major bioactive compound in aged black garlic with multiple pharmacological benefits, including antioxidant and neuroprotective effects; however, the underlying molecular mechanisms of these benefits remain unclear. In our previous study, we demonstrated that cystathionine γ-lyase (CSE), a sulfur-containing amino acid-metabolizing enzyme involved in the transsulfuration pathway, metabolizes S-nitroso-L-cysteine via a C-S lyase reaction. In this study, we investigated whether CSE-mediated metabolism is involved in the physiological effects of various cysteine derivatives, including SAC. We evaluated the potential of a series of S-alkylcysteine derivatives with varying alkyl chain lengths and degrees of unsaturation as CSE substrates. Recombinant CSE experiments revealed that thiol compounds were produced from propyl derivatives, whereas supersulfides were generated from ethyl, propyl, and allyl derivatives. Kinetic analysis demonstrated that the allyl derivative exhibited a stronger substrate affinity than the propyl derivative, similar to that of the endogenous substrate cystathionine. This study suggests a novel molecular basis for CSE-mediated metabolism and subsequent supersulfide production, which contributes to the diverse health-promoting effects of SAC in mammalian tissues.