Cysteine derivatives, metabolism

Shimabukuro et al. (1971), investigating the metabolism of atrazine in maize, found that the tolerance of maize is not brought about by the above nonenzymatic inactivation alone, but that the primary factor is an enzyme, which conjugates triazine with glutathione, which is then converted to the glutamyl-S-cysteine derivative ... 

In mammals, peptide hormones typically contain only the a-amino acids of proteins finked by standard peptide bonds. Other peptides may, however, contain nonprotein amino acids, derivatives of the protein amino acids, or amino acids finked by an atypical peptide bond. For example, the amino terminal glutamate of glutathione, which participates in protein folding and in the metabolism of xenobiotics (Chapter 53), is finked to cysteine by a non-a peptide bond (Figure 3—3). The amino terminal glutamate of thyrotropin-... 

S-Nitroso derivatives of the biological thiols—glutathione, cysteine (115) and homocysteine—have been considered as bioactive intermediates in the metabolism of organic nitrates and the endothelium-derived relaxing factor with properties of nitric oxide. A simple, rapid and reproducible method for separating these thiols from their... 

The conversion of the glutathione conjugate to its cysteinyl derivative is mediated, at least in part, by enzymes in the intestinal epithelial cells. S-(Pentachlorobutadienyl)glutathione and S-(pentachlorobutadienyl)-L-cysteine are partially reabsorbed from the intestines and transported to the liver and subsequently to the body tissues (Gietl et al. 1991). Only a portion of the reabsorbed material is taken up by the liver for additional metabolism. When liver uptake of the glutathione conjugate was measured using perfused rat livers, the maximum uptake observed was 39% (Koob and Dekant 1992). A portion of this material was re-excreted in bile without any metabolic... 

Acetaldehyde is oxidized to acetic acid by NAD+-dependent aldehyde dehydrogenases (ALDH) in liver and nasal mucosal preparations. Its administration to rats causes an increase in urinary excretion of sulfur metabolites and it is known to react with cysteine to produce a thiazolidine 4-carboxylic acid derivative that can be A -nitro-sated in vivo upon co-administration of nitrite (lARC, 1985). Many studies have been published subsequently, but these have been mainly in the context of ethanol metabolism. 

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