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  • Title: Cell-mediated biotransformation of S-nitrosoglutathione.
    Author: Gordge MP, Addis P, Noronha-Dutra AA, Hothersall JS.
    Journal: Biochem Pharmacol; 1998 Mar 01; 55(5):657-65. PubMed ID: 9515576.
    Abstract:
    Spontaneous release of nitric oxide (NO) from S-nitrosothiols cannot explain their bioactivity, suggesting a role for cellular metabolism or receptors. Using immortalised cells and human platelets, we have identified a cell-mediated mechanism for the biotransformation of the physiological S-nitrosothiol compound S-nitrosoglutathione (GSNO) into nitrite. We suggest the name "GSNO lyase" for this activity. GSNO lyase activity varied between cell types, being highest in a fibroblast cell line and lowest in platelets. In NRK 49F fibroblasts, GSNO lyase mediated a saturable, GSNO concentration-dependent accumulation of nitrite in conditioned medium, which was inhibited both by transition metal chelators, and by subjecting cells to oxidative stress using a combination of the thiol oxidant diamide and Zn2+, a glutathione reductase inhibitor. Activity was resistant, however, to both acivicin, an inhibitor of gamma-glutamyl transpeptidase (EC 2.3.2.2), and to ethacrynic acid, an inhibitor of Pi class glutathione-S-transferases (EC 2.5.1.18), thus neither of these enzymes could account for NO release. Although GSNO lyase does not explain the platelet-selective pharmacological properties of GSNO, cellular biotransformation suggests therapeutic avenues for targeted delivery of NO to other tissues.
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