title: Molecular and cellular mechanism of the effect of La(III) on horseradish peroxidase.
abstract: Horseradish is an important economic crop. It contains horseradish peroxidase (HRP) and lots of nutrients, and has specific pungency. Lanthanum is one of the heavy metals in the environment. It can transfer through the food chain to humans. In this paper, the molecular and cellular mechanism of the toxic effects of La(III) on HRP in vivo was investigated with an optimized combination of biophysical, biochemical, and cytobiological methods. It was found that La(III) could interact with O and/or N atoms in the backbone/side chains of the HRP molecule in the cell membrane of horseradish treated with 80 microM La(III), leading to the formation of a new complex of La and HRP (La-HRP). The formation of the La-HRP complex causes the redistribution of the electron densities of atoms in the HRP molecule, especially the decrease in the electron density of the active center, Fe(III), in the heme group of the La-HRP molecule compared with the native HRP molecule in vivo. Therefore, the electron transfer and the activity of HRP in horseradish treated with 80 microM La(III) are obviously decreased compared with those of the native HRP in vivo. This is a possible molecular and cellular mechanism for the toxic effect of La(III) on HRP in vivo. It is suggested that the accumulation of La in the environment, especially the formation of the La-HRP complex in vivo, is harmful to organisms.
authors.affiliation: Jiangsu Key Laboratory of Biofunctional Materials, College of Chemistry and Environmental Science, Nanjing Normal University, Nanjing, 210046, People's Republic of China.
authors.forename: Lihong
authors.initials: L
authors.lastname: Wang
authors.forename: Qing
authors.initials: Q
authors.lastname: Zhou
authors.forename: Tianhong
authors.initials: T
authors.lastname: Lu
authors.forename: Xiaolan
authors.initials: X
authors.lastname: Ding
authors.forename: Xiaohua
authors.initials: X
authors.lastname: Huang
mesh_terms: D031215:Armoracia / Q000166:cytology / Q000201:enzymology*; D004563:Electrochemistry; D006735:Horseradish Peroxidase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007811:Lanthanum / Q000737:chemistry*; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D013499:Surface Properties
chemical_list: D010940:Plant Proteins; D007811:Lanthanum; D006735:Horseradish Peroxidase