title: Phospholipid hydroperoxide glutathione peroxidase activity of human glutathione transferases.
abstract: Human glutathione transferases (GSTs) from Alpha (A), Mu (M) and Theta (T) classes exhibited glutathione peroxidase activity towards phospholipid hydroperoxide. The specific activities are in the order: GST A1-1>GST T1-1>GST M1-1>GST A2-2>GST A4-4. Using a specific and sensitive HPLC method, specific activities towards the phospholipid hydroperoxide,1-palmitoyl-2-(13-hydroper oxy-cis-9, trans-11 -octadecadienoyl)-l-3-phosphatidylcholine (PLPC-OOH) were determined to be in the range of 0.8-20 nmol/min per mg of protein. Two human class Pi (P) enzymes (GST P1-1 with Ile or Val at position 105) displayed no activity towards the phospholipid hydroperoxide. Michaelis-Menten kinetics were followed only for glutathione, whereas there was a linear dependence of rate with PLPC-OOH concentration. Unlike the selenium-dependent phospholipid hydroperoxide glutathione peroxidase (Se-PHGPx), the presence of detergent inhibited the activity of GST A1-1 on PLPC-OOH. Also, in contrast with Se-PHGPx, only glutathione could act as the reducing agent for GST A1-1. A GST A1-1 mutant (Arg15Lys), which retains the positive charge between the GSH- and hydrophobic binding sites, exhibited a decreased kcat for PLPC-OOH but not for CDNB, suggesting that the correct topography of the GSH site is more critical for the phospholipid substrate. A Met208Ala mutation, which gives a modified hydrophobic site, decreased the kcat for CDNB and PLPC-OOH by comparable amounts. These results indicate that Alpha, Mu and Theta class human GSTs provide protection against accumulation of cellular phospholipid hydroperoxides.
authors.affiliation: Department of Biochemistry, Institute of Food Research, Norwich Laboratory, Norwich Research Park, Colney, Norwich NR4 7UA, UK.
authors.forename: R
authors.initials: R
authors.lastname: Hurst
authors.forename: Y
authors.initials: Y
authors.lastname: Bao
authors.forename: P
authors.initials: P
authors.lastname: Jemth
authors.forename: B
authors.initials: B
authors.lastname: Mannervik
authors.forename: G
authors.initials: G
authors.lastname: Williamson
mesh_terms: D001665:Binding Sites / Q000502:physiology; D004137:Dinitrochlorobenzene / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D005979:Glutathione Peroxidase / Q000378:metabolism*; D005982:Glutathione Transferase / Q000145:classification / Q000378:metabolism*; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D007700:Kinetics; D008054:Lipid Peroxides / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D000080662:Phospholipid Hydroperoxide Glutathione Peroxidase; D010743:Phospholipids / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism
chemical_list: D004137:Dinitrochlorobenzene; D007527:Isoenzymes; D008054:Lipid Peroxides; D010743:Phospholipids; D011994:Recombinant Proteins; D000080662:Phospholipid Hydroperoxide Glutathione Peroxidase; D005979:Glutathione Peroxidase; D005982:Glutathione Transferase; D005978:Glutathione