Cysteine monoxide

Male Sprague Dawley rats, seven days post weanling (Bantin and Kingman, Inc., Fremont, CA) were fed pelleted rodent chow (5001, Ralston Purina Co., St. Louis, MO) or modified AIN-76 diets (BioServ, Inc., Frenchtown, NJ) with or without added sulfur amino acids. Chow, diets, and water were supplied to the rats ad libitum. The AIN-76 diet (16) was modified to contain 12% casein (normally 20% casein), and the weight difference made up with cornstarch. The normal methionine supplement was not included. The cornstarch and sucrose portions were held separately from the casein/vitamin/mineral (CVM) mixture for the purpose of mixing amino acids with the cornstarch and sucrose (CsS). Methionine (MET), methionine sulfoxide (MSO) and cysteine sulfinic acid (CSA) were obtained from Sigma Chemical Co., St. Louis, MO. Cysteine monoxide (CMO) was prepared by the method of Savige et al., (17). 

The microsomes from the CMO-fed rats produced the most striking differences in metabolic profile compared to the control microsomes. The data shown in Table III and Fig 3 (for clarity) demonstrate that microsomes from animals fed the cysteine monoxide diet (AIN/CMO) are far more efficient at metabolizing BaP (more BaP oxidized per mole cytochrome P-450/unit time) than are microsomes from rats fed the control diet (AIN/MET). Lower recovery of BaP and metabolites was obtained from the microsomes of the AIN/CMO-fed rats compared to the AIN/M-fed rats (87 to 91%) and a control run containing no NADPH (94% recovery). This result is probably due to the fact that the tetrols and the unknown metabolite, both present in much greater amounts in the CMO case than in the MET (control) case, are not quantifiable, and thus have not been considered in the calculations. Microsomes from the chow-fed rats behaved similarly to the microsomes from AIN/CMO-fed rats, while the other cases showed intermediate values of recovery (data not shown). In every case,... 

The carbon monoxide dehydrogenase of the aerobe Oligotropha carboxidovorans contains both Cu and Mo in the form of a cluster in which the Mo is bound to the thiol groups of molybdopterin cytosine nucleotide, and the Cu to cysteine residue in the form of a Cu-S-Mo(=0)OFl cluster (Dobbek et al. 2002). 

The sulphite aftertreatment is particularly important with permonosulphuric acid treatment. Evidence for the underlying mechanism is available from analysis of sulphur oxidation products formed in the various processes (Table 10.34). It is evident from these results that the concentration of RSS()5 anionic groups necessary to change the hydration of the fibre surface is achieved by the reaction of bisulphite with cystine monoxide residues to give the required cysteine-S-sulphonate groups [311]. 

Elfarra, A.A., Sharer, J.E. Duescher, R.J. (1995) Synthesis and characterization of Wacetyl-L-cysteine S-conjugates of butadiene monoxide and their detection and quantitation in urine of rats and mice given butadiene monoxide. Chem. Res. Toxicol.. 8, 68-76... 

Figure 9.3. The cytochrome P450 active site containing the heme iron with six ligands. Four ligands are occupied by nitrogens from the protoporphyrin IX moiety. The fifth ligand is occupied by a sulfur from the invariant cysteine. The sixth ligand is occupied by oxygen, carbon monoxide, or water.

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