Cysteine lyase sulfoxide derivatives

S-Alkylcysteine C-S Lyase (EC 4.4.1.6). The endosperm of seeds of the shrub Albizzia lophanta contains djenkolic acid (HOOCCH(NH2)-CH2SCH2SCH2CH(NH2)C00H) and an enzyme which cleaves it to pyruvate, ammonia, and highly odoriferous substances (CH2(SH)2 ) (48, 49). The enzyme has been purified 200-fold by acid and heat treatment, (NH4)2S04 precipitation, and adsorption on alumina (50). It has a broad specificity and cleaves S-derivatives of L-cysteine, its sulfoxide, and sulfone. L-Cysteine itself is cleaved to pyruvate, HjS, and ammonia. 

LC/MS/MS is an important technique for the analysis of free metabolites and covalent adducts of sulfur mustard in urine and blood. In the case of TDG and TDGO, LC/MS has not yet been able to achieve the LODs obtainable with GC/MS after derivatization. LC/MS/MS has, however, been used successfully to analyze the metabolites (20, 21) derived from an initial reaction of sulfur mustard with glutathione (see Chapter 16). The two metabolites (20), derived from the 3-lyase pathway, can be isolated from urine by SPE on a hydroxylated polystyrene-divinylbenzene polymeric cartridge. Using a sensitive triple sector quadrupole LC/MS/MS system, detection limits of O.lng/ml have been achieved using positive ESI and MRM (56). This provides a useful alternative to GC/MS/MS, which requires reduction of the sulfoxide functions with titanium trichloride. An LC/MS/MS method (detection limit lng/ml) has been developed for the analysis of the hisf N - ace ly I cysteine) metabolite (21) in urine (57). Concentration from acidified urine was achieved on... 

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