title: Hydrolysis of glutathione by human liver gamma-glutamyltransferase.
abstract: We studied the catalytic hydrolysis of glutathione by human liver gamma-glutamyltransferase [(gamma-glutamyl)-peptide:amino acid gamma-glutamyltransferase, EC 2.3.2.2]. Glutamate production from glutathione was maximal at pH 7.4 (37 degrees C). Kinetically, the liver enzyme is similar to human kidney gamma-glutamyltransferase: their respective Km values with glutathione as substrate are similar (0.096 x 10(-3) mol/L and 0.097 x 10(-3) mol/L, respectively). S-Methylglutathione was hydrolyzed at a slightly higher rate than glutatione by liver gamma-glutamyltransferase. From these findings and other established properties of liver and kidney gamma-glutamyltransferase we propose that human liver is an important site of glutathione catabolism and that gamma-glutamyltransferase in liver catalyzes the first step of the catabolism of glutathione and glutathione conjugates in this organ.
mesh_terms: D005978:Glutathione; D006801:Humans; D006868:Hydrolysis; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008298:Maleates / Q000494:pharmacology; D005723:gamma-Glutamyltransferase / Q000378:metabolism*
chemical_list: D008298:Maleates; D005723:gamma-Glutamyltransferase; D005978:Glutathione