Cysteine conjugates thiol formation from

Thiol Formation. Thiol formation from cysteine conjugates has been known since 1951 (57), toxicity of the thiol formed durinq dichlorovinylcyst ne metabolism was reported in 1957 (15), and the enzyme involved was termed a "thionase" in 1965 (58). The enzyme(s) is now called a cysteine conJugate-8-lyase (C-S lyase) and has been purified from rat liver (59,60), partially purified from microorganisms (61,62) shown to function in the intestinal microflora (9,49), and in kidney (63). The general reaction catalyzed by C-S lyase is shown in Equation 11. 

Sulfoxidation. Sulfoxidation Is common in sulfur biochemistry (43,44), and has been observed with many of the transamination products listed in Table III, with mercapturic acids (45,46,47) and cysteine conjugates (12). Sulfoxidation is also common with the methylthio-containing metabolites produced from cysteine conjugates (see "Thiol Formation" below). Sulfoxidation increases the polarity of compounds and therefore affects their excretability. 

Since ferulic acid (free or bound), the precursor of PVG, contains an activated double bond conjugated to a carboxylic acid and to a phenyl ring, we hypothesized that it may also be sensitive to the nucleophilic attack by thiols, thereby inhibiting PVG formation. Pasteurized SSOJ samples (20 mL) were fortified with L-cysteine or N-acetyl-L-cysteine and stored at 45°C for 14 days (28). In addition, SSOJ samples were also stored for six weeks at 4, 15, 25 and 35°C. Extraction of PVG from the incubated SSOJ samples was performed, and samples were analyzed for PVG by HPLC. 

---