title: Spectrophotometric investigations with hexa-coordinate ferric lignin peroxidase: does water retention at the active site influence catalysis?
abstract: Native lignin peroxidase (LIP) can adopt either a stable penta- or hexa-coordinate state. We have examined catalysis with hexa-coordinate ferric LIP as the starting material, using rapid scanning spectrophotometry. Initial two-electron oxidation of hexa-coordinate native LIP by H(2)O(2) (Compound I formation) was accompanied by a shifting isosbestic point (419-->416 nm), consistent with displacement of a resident water molecule, prior to the reaction of the ferric iron with H(2)O(2). The Compound I species derived from a hexa-coordinate ferric state shows an unusual peak at 520 nm, which may be due to water retention in the vicinity of the heme active site. Compound I reduction by veratryl alcohol showed saturation kinetics, which contrasts with the situation observed when Compound I is derived from a penta-coordinate ferric state. The data inferred that water can interfere with heme access by electron donors, altering the mechanism of Compound I reduction.
authors.affiliation: Department of Chemical and Life Sciences, University of Greenwich, SE18 6PF, London, UK.
authors.forename: Thomas B
authors.initials: TB
authors.lastname: Brück
authors.forename: Patricia J
authors.initials: PJ
authors.lastname: Harvey
mesh_terms: D001592:Benzyl Alcohols / Q000378:metabolism; D001665:Binding Sites; D002384:Catalysis; D005290:Ferric Compounds / Q000737:chemistry / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D016877:Oxidants / Q000378:metabolism; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000737:chemistry* / Q000378:metabolism*; D013053:Spectrophotometry; D014867:Water / Q000737:chemistry*
chemical_list: D001592:Benzyl Alcohols; D005290:Ferric Compounds; D016877:Oxidants; D014867:Water; D006861:Hydrogen Peroxide; D010544:Peroxidases; C042858:lignin peroxidase; C042197:veratryl alcohol