Cysteinylglycine

This reaction helps transfer certain amino acids across the plasma membrane, the amino acid being subse-quendy hydrolyzed from its complex with GSH and the GSH being resynthesized from cysteinylglycine. The enzyme catalyzing the above reaction is 7-glu-tamyltransferase (GGT). It is present in the plasma membrane of renal mbular cells and bile ducmle cells, and in the endoplasmic reticulum of hepatocytes. The enzyme has diagnostic value because it is released into the blood from hepatic cells in various hepatobihary diseases. 

Glutathione + amino acid —> y-glutamyl-amino acid + cysteinylglycine... 

The reactivity of mechlorethamine was also examined in the presence of reduced glutathione (L-glutamyl-L-cysteinylglycine), a major cytoprotective compound present throughout the body in physiologically high concentra-... 

Fig. 11.5. Mechanism of hydrolytic dechlorination of mechlorethamine (11.31, R = Me) and other antitumor nitrogen mustards [65] [66]. Also shown is the mechanism of the nonenzymat-ic conjugation with reduced glutathione (GSH, L-glutamyl-L-cysteinylglycine).

Fig. 2.2.4 Chromatogram of SBDF-derivatised thiols in human plasma, a Cysteine, b cysteamine, c cysteinylglycine, d Hey...

The separation obtained with a normal plasma sample is shown in Fig. 2.2.4. The order of elution is cysteine (3.5 min), cysteamine (4.0 min), cysteinylglycine (5.0 min) and Hey (6.5 min) with a peak width of under 1 min and complete resolution of peaks. 

Cilastatin prevents the metabolism of imipenem by renal tubular dipeptidase, which also hydrolyses the glutathione metabolite cysteinylglycine. In patients taking imipenem + cilastatin, plasma concentrations of cysteinylglycine were significantly increased, while cysteine concentrations fell and homocysteine concentrations were unchanged (483). The clinical significance of this is not clear. 

Badiou S, Bellet H, Lehmann S, Cristol JP, Jaber S. Elevated plasma cysteinylglycine levels caused by cilasta-tin-associated antibiotic treatment. Clin Chem Lab Med 2005 43(3) 332-4. 

Figure 4.6 Typical stop-flow 1 H LC-NMR data obtained showing the cysteinylglycine adduct of a non-nucleoside reverse-transcriptase inhibitor from a sample of rat bile...

These data provide unambiguous proof of structure for three metabolites of efavirenz, the major metabolite 8-O-glucuronide conjugate, (9), the novel hydroxylated cyclopropyl, 8-O-sulfate, cysteinylglycine di-conjugate (8), and... 

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