Valine 10 may act as a driver for product release from the active site of human glutathione transferase P1-1

Abstract

We have probed the electrophilic binding site (H-site) of human glutathione transferase P1-1 through mutagenesis of two valines, Val 10 and Val 35, into glycine and alanine, respectively. These two residues were previously shown to be the only conformationally variable residues in the H-site and hence may play important roles in cosubstrate recognition and/or product dissociation. Both of these mutant enzymes have been expressed in Escherichia coli and purified and their kinetic properties characterized. The results demonstrate that Val35Ala behaves similarly to wild-type, whereas Val10Gly exhibits a strong decrease of k(cat) and k(cat)/K(m) (cosub) toward two selected cosubstrates: ethacryn..