Oxidation of indole-3-acetic acid by dioxygen catalysed by plant peroxidases: specificity for the enzyme structure.
Indole-3-acetic acid (IAA) can be oxidized via two mechanisms: a conventional hydrogen-peroxide-dependent pathway, and one that is hydrogen-peroxide-independent and requires oxygen. It has been shown here for the first time that only plant peroxidases are able to catalyse the reaction of IAA oxidation with molecular oxygen. Cytochrome c peroxidase (CcP), fungal peroxidases (manganese-dependent peroxidase, lignin peroxidase and Arthromyces ramosus peroxidase) and microperoxidase were essentially inactive towards IAA in the absence of added H2O2. An analysis of amino acid sequences allowed five structurally similar fragments to be identified in auxin-binding proteins and plant peroxidases. The corresponding fragments in CcP and fungal peroxidases showed no similarity with auxin-binding proteins. Five structurally similar fragments form a subdomain including the catalytic centre and two residues highly conserved among 'classical' plant peroxidases only, namely His-40 and Trp-117. The subdomain identified above with the two residues might be responsible for the oxidation of the physiological substrate of classical plant peroxidases, IAA.
Savitsky
P A
PA
Department of Chemical Enzymology, Chemical Faculty, Moscow State University, Moscow 119899 GSP, Russia.
Gazaryan
I G
IG
Tishkov
V I
VI
Lagrimini
L M
LM
Ruzgas
T
T
Gorton
L
L
D000595:Amino Acid Sequence; D020134:Catalytic Domain; D002851:Chromatography, High Pressure Liquid; D017124:Conserved Sequence / Q000235:genetics / Q000502:physiology; D005656:Fungal Proteins / Q000737:chemistry / Q000378:metabolism; D006420:Hemeproteins / Q000737:chemistry / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007210:Indoleacetic Acids / Q000378:metabolism*; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016877:Oxidants / Q000378:metabolism*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism*; D010544:Peroxidases / Q000737:chemistry / Q000378:metabolism*; D010937:Plant Growth Regulators; D010940:Plant Proteins; D010944:Plants / Q000201:enzymology*; D011487:Protein Conformation; D011956:Receptors, Cell Surface; D013329:Structure-Activity Relationship
D005656:Fungal Proteins; D006420:Hemeproteins; D007210:Indoleacetic Acids; D016877:Oxidants; D010937:Plant Growth Regulators; D010940:Plant Proteins; D011956:Receptors, Cell Surface; C046131:auxin receptor, plant; C030737:indoleacetic acid; D006861:Hydrogen Peroxide; D010544:Peroxidases; D010100:Oxygen