S-nitrosoglutathione (GSNO) is a nitric oxide (NO) donor compound which has been postulated to be involved in transport of NO in vivo. It is known that gamma-glutamyl transpeptidase (GGT) is one of the enzymes involved in the enzyme-mediated decomposition of GSNO, but no kinetics studies of the reaction GSNO-GGT are reported in literature. In this study we directly investigated the kinetics of GGT with respect to GSNO as a substrate and glycyl-glycine (GG) as acceptor co-substrate by spectrophotometry at 334 nm. GGT hydrolyses the gamma-glutamyl moiety of GSNO to give S-nitroso-cysteinylglycine (CGNO) and gamma-glutamyl-GG. However, as both the substrate GSNO and the first product CGNO absorb at 334 nm, we optimized an ancillary reaction coupled to the enzymatic reaction, based on the copper-mediated decomposition of CGNO yielding oxidized cysteinyl-glycine and NO. The ancillary reaction allowed us to study directly the GSNO/GGT kinetics by following the decrease of the characteristic absorbance of nitrosothiols at 334 nm. A K(m) of GGT for GSNO of 0.398+/-31 mM was thus found, comparable with K(m) values reported for other gamma-glutamyl substrates of GGT.

A kinetic study of gamma-glutamyltransferase (GGT)-mediated S-nitrosoglutathione catabolism

TACITO, ALESSIA;PAOLICCHI, ALDO;BARSACCHI, RENATA;FRANZINI, MARIA;VECOLI, CECILIA;POMPELLA, ALFONSO;
2009-01-01

Abstract

S-nitrosoglutathione (GSNO) is a nitric oxide (NO) donor compound which has been postulated to be involved in transport of NO in vivo. It is known that gamma-glutamyl transpeptidase (GGT) is one of the enzymes involved in the enzyme-mediated decomposition of GSNO, but no kinetics studies of the reaction GSNO-GGT are reported in literature. In this study we directly investigated the kinetics of GGT with respect to GSNO as a substrate and glycyl-glycine (GG) as acceptor co-substrate by spectrophotometry at 334 nm. GGT hydrolyses the gamma-glutamyl moiety of GSNO to give S-nitroso-cysteinylglycine (CGNO) and gamma-glutamyl-GG. However, as both the substrate GSNO and the first product CGNO absorb at 334 nm, we optimized an ancillary reaction coupled to the enzymatic reaction, based on the copper-mediated decomposition of CGNO yielding oxidized cysteinyl-glycine and NO. The ancillary reaction allowed us to study directly the GSNO/GGT kinetics by following the decrease of the characteristic absorbance of nitrosothiols at 334 nm. A K(m) of GGT for GSNO of 0.398+/-31 mM was thus found, comparable with K(m) values reported for other gamma-glutamyl substrates of GGT.
2009
Angeli, Valeria; Tacito, Alessia; Paolicchi, Aldo; Barsacchi, Renata; Franzini, Maria; Baldassini, Riccardo; Vecoli, Cecilia; Pompella, Alfonso; Bramanti, Emilia
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11568/757503
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