title: The reduction potential of lactoperoxidase.
abstract: The reduction potential of Fe(III)/Fe(II) lactoperoxidase has been determined. Optical determinations of equilibria with 2-methyl-3-hydroxy-1,4-naphthoquinone as indicator and prereduced 9,10-anthraquinone-2-sulfonate as reducing agent gave Em,7.0 = -191 +/- 2 mV. Potentiometric determinations with 9,10-anthraquinone-2-sulfonate as mediator and, in the reduced form as reducing agent, gave Em,7.0 = -188 +/- 1 mV. Addition of 0.5% N-cetyl-N,N,N-trimethyl-ammonium bromide, and using dithionite as reducing agent, gave Em,7.0 = -183 mV and -179 mV with 9,10-anthraquinone-2-sulfonate and 9,10-anthraquinone-2,6-disulfonate, respectively, as mediators.
mesh_terms: D000818:Animals; D002417:Cattle; D004227:Dithionite; D007784:Lactoperoxidase / Q000378:metabolism*; D008892:Milk / Q000201:enzymology; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000378:metabolism*; D011199:Potentiometry / Q000379:methods; D013055:Spectrophotometry, Infrared; D013431:Sulfates
chemical_list: D013431:Sulfates; D004227:Dithionite; D007784:Lactoperoxidase; D010544:Peroxidases