title: Kinetic characterization of a basic peroxidase from garlic (Allium sativum L.) cloves.
abstract: Peroxidases catalyze the reduction of H(2)O(2) by taking electrons from a variety of compounds from the secondary metabolism including flavonoids and lignin precursors. This work describes the purification and kinetic characterization of a basic peroxidase from garlic cloves using quercetin and p-coumaric acid, flavonoid and phenolic compounds found in garlic cloves. The high catalytic efficiency shown by this basic peroxidase in the oxidation of quercetin at acidic pH suggests good adaptation of this enzyme, involved in quercetin catabolism in the acidic physiological pH conditions of the vacuoles, where it is presumably located. Likewise, garlic peroxidase showed similar oxidation rates for hydroxycinnamyl (p-coumaric) and sinapyl-type structures, which suggests its involvement in the cross-coupling reactions that occur in the cell wall during lignification. On the other hand, the high affinity of this enzyme for H(2)O(2) would be in accordance with the oxidation of both flavonoid and phenolic compounds to regulate H(2)O(2) levels in tissues/organelles, where this peroxidase is expressed.
authors.affiliation: Dept. of Plant Biology, Faculty of Biology, Univ. of Murcia, Campus de Espinardo, E-30100 Murcia, Spain.
authors.forename: Saida Medjeldi
authors.initials: SM
authors.lastname: Marzouki
authors.forename: Lorena
authors.initials: L
authors.lastname: Almagro
authors.forename: Ana B
authors.initials: AB
authors.lastname: Sabater-Jara
authors.forename: Alfonso
authors.initials: A
authors.lastname: Ros Barceló
authors.forename: María A
authors.initials: MA
authors.lastname: Pedreño
mesh_terms: D000975:Antioxidants / Q000378:metabolism; D003373:Coumaric Acids / Q000032:analysis / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005737:Garlic / Q000737:chemistry / Q000201:enzymology*; D006861:Hydrogen Peroxide / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008031:Lignin / Q000032:analysis / Q000378:metabolism; D010084:Oxidation-Reduction; D009195:Peroxidase / Q000378:metabolism*; D010636:Phenols / Q000032:analysis / Q000378:metabolism; D010936:Plant Extracts / Q000737:chemistry; D011422:Propionates; D011794:Quercetin / Q000032:analysis / Q000378:metabolism
chemical_list: D000975:Antioxidants; D003373:Coumaric Acids; D010636:Phenols; D010936:Plant Extracts; D011422:Propionates; D008031:Lignin; D011794:Quercetin; D006861:Hydrogen Peroxide; D009195:Peroxidase; C495469:p-coumaric acid