title: Peroxidase-catalyzed oxidative coupling of paraphenylenediamine with 3-dimethylaminobenzoic acid: application in crude plant extracts.
abstract: This paper presents a novel spectrophotometric method to measure peroxidase activity using paraphenylenediamine dihydrochloride (PPDD) and 3-dimethylaminobenzoic acid (DMAB). The PPDD traps free radicals and becomes oxidized to electrophillic 1,4-diimine, which couples with DMAB to give an intense green-colored chromogenic species with maximum absorbance at 710 nm. This assay was adopted for the quantification of hydrogen peroxide between 5 and 45 microM. From the kinetic data, a two-substrate ping-pong mechanism of peroxidase was established. The catalytic efficiency and catalytic constant (k(cat)) of the proposed assay were 0.54 x 10(6) M(-1) min(-1) and 0.0436 x 10(3) min(-1), respectively. As a simple, rapid, precise, and sensitive technique, PPDD-DMAB stands as a potential replacement for the traditional guaiacol method. Application of this method in plant extracts opens its relevance in the field of biochemical analysis.
authors.affiliation: Department of Studies in Chemistry, University of Mysore, Manasagangotri, Mysore, India. drpn58@yahoo.co.in
authors.forename: Padmarajaiah
authors.initials: P
authors.lastname: Nagaraja
authors.forename: Anantharaman
authors.initials: A
authors.lastname: Shivakumar
authors.forename: Ashwinee Kumar
authors.initials: AK
authors.lastname: Shrestha
mesh_terms: D062365:Aminobenzoates / Q000737:chemistry*; D002384:Catalysis; D007700:Kinetics; D010084:Oxidation-Reduction; D009195:Peroxidase / Q000737:chemistry*; D010655:Phenylenediamines / Q000737:chemistry*; D010936:Plant Extracts / Q000737:chemistry*; D010940:Plant Proteins / Q000737:chemistry*; D010944:Plants / Q000737:chemistry; D013053:Spectrophotometry / Q000379:methods*; D062368:meta-Aminobenzoates
chemical_list: C543405:3-dimethylaminobenzoic acid; D062365:Aminobenzoates; D010655:Phenylenediamines; D010936:Plant Extracts; D010940:Plant Proteins; D062368:meta-Aminobenzoates; D009195:Peroxidase; C029728:4-phenylenediamine