title: Electroactive centers in Euphorbia latex and lentil seedling amine oxidases.
abstract: The electrochemical behavior of redox centers in the active site of amine oxidases from lentil seedlings and Euphorbia characias latex was investigated using a mercury film electrode. Tyrosine-derived 6-hydroxydopa quinone (TPQ) and copper ions in the active site are redox centers of these amine oxidases. The enzymes undergo two reduction processes at negative potentials related to the reduction of the TPQ cofactor to the corresponding hydroquinones and the reduction of copper ions, (Cu(II)-->Cu(I)). Copper depleted enzymes, prepared by reduction with dithionite followed by dialysis against cyanide, undergo only one reduction process. Nyquist diagrams, recorded at potentials corresponding to the reduction of cofactors as dc-offset, represent charge transfer impedance followed by a Warburg-type line at low frequencies, indicating the occurrence of a diffusion controlled process in the rate-limiting step of the reduction process.
authors.affiliation: Institute of Biochemistry and Biophysics, University of Tehran, Tehran, Iran.
authors.forename: Hossein
authors.initials: H
authors.lastname: Heli
authors.forename: Mojtaba
authors.initials: M
authors.lastname: Amani
authors.forename: Ali Akbar
authors.initials: AA
authors.lastname: Moosavi-Movahedi
authors.forename: Ali
authors.initials: A
authors.lastname: Jabbari
authors.forename: Giovanni
authors.initials: G
authors.lastname: Floris
authors.forename: Anna
authors.initials: A
authors.lastname: Mura
mesh_terms: D006631:Amine Oxidase (Copper-Containing) / Q000737:chemistry / Q000378:metabolism*; D000594:Amino Acid Oxidoreductases / Q000737:chemistry / Q000378:metabolism; D000595:Amino Acid Sequence; D001665:Binding Sites; D003300:Copper / Q000378:metabolism; D004295:Dihydroxyphenylalanine / Q000031:analogs & derivatives / Q000032:analysis; D004563:Electrochemistry; D004566:Electrodes; D028481:Euphorbia / Q000201:enzymology*; D007700:Kinetics; D027806:Lens Plant / Q000201:enzymology*; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism; D036226:Seedlings / Q000201:enzymology*
chemical_list: D010940:Plant Proteins; D004295:Dihydroxyphenylalanine; C067626:6-hydroxydopa quinone; D003300:Copper; D000594:Amino Acid Oxidoreductases; D006631:Amine Oxidase (Copper-Containing)