RCH₂NH₂ + O₂ + H₂O à RCHO+NH₃ +H₂O₂. 

Relatively abundant comprising at least 0.1% total soluble protein in etiolated pea seedling epicotyls.  Its function remains unclear.  Plant copper amine oxidases are generally found in the apoplast, loosely associated with the cell wall.  Oxidation of di and polyamines present within the apoplast and the H2O2 formed by their oxidation may be important in lignosuberization and cross-linking of extracellular macromolecules such as extensisns.  They may play a role in the defense response along with peroxidases.

Abstracts of interesting papers: Related Articles, Books 

Developmental expression and biochemical analysis of the Arabidopsis atao1 gene encoding an H2O2-generating diamine oxidase.

Moller SG, McPherson MJ.

Centre for Plant Biochemistry and Biotechnology, University of Leeds, UK.

A copper amine oxidase encoding gene, atao1, has been isolated and characterized from Arabidopsis thaliana. Sequence analysis reveals that atao1 encodes a 668 amino acid polypeptide (ATAO1) with 48% identity to copper amine oxidases from pea and lentil. The promoter region of atao1 was transcriptionally fused with the reporter genes encoding beta-glucuronidase and modified green fluorescent protein. Analysis of transgenic Arabidopsis together with in situ hybridization of wild-type plants reveals temporally and spatially discrete patterns of gene expression in lateral root cap cells, vascular tissue of roots, developing leaves, the hypocotyl, and in the style/stigmatal tissue. Enzyme activity assays show that ATAO1 preferentially oxidizes the aliphatic diamine putrescine with production of the corresponding aldehyde, ammonia and hydrogen peroxide, a recognized plant signal molecule and substrate for peroxidases. Histochemical analysis reveals that atao1 expression in developing tracheary elements precedes and overlaps with lignification and therefore is a good marker for vascular development. In both vascular tissue and the root cap, atao1 expression occurs in cells destined to undergo programmed cell death.

Molecular cloning and heterologous expression of pea seedling copper amine oxidase.

Koyanagi T, Matsumura K, Kuroda S, Tanizawa K.

Department of Structural Molecular Biology, The Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Japan.

The cDNA coding for copper amine oxidase has been cloned from etiolated pea seedlings (Pisum sativum). The deduced amino acid sequence, consisting of 674 residues including the signal peptide, agreed well with those reported for the enzymes from a different cultivar of P. sativum and other plant sources, except for several evolutionary replacements located mostly on the molecular surface. A heterologous expression system for the cloned pea enzyme was constructed with the yeast Pichia pastoris, using the AOX1 promoter and the yeast alpha-factor secretion signal. Adding copper to the culture medium increased the secretion of an active, quinone-containing enzyme. Furthermore, the inactive enzyme produced in a copper-deficient medium was activated considerably by subsequent incubation with excess cupric ions. These results strongly suggest that the Tyr-derived redox cofactor, 2,4,5-trihydroxyphenylalanylquinone (topa quinone, TPQ), is produced in the plant enzyme by post-translational modification that proceeds through the copper-dependent, self-processing mechanism, as in the enzymes from bacteria and yeast.

Plant Cell Physiol 2000 Nov;41(11):1259-66

Phenylethylamine-induced generation of reactive oxygen species and ascorbate free radicals in tobacco suspension culture: mechanism for oxidative burst mediating Ca2+ influx.

Kawano T, Pinontoan R, Uozumi N, Morimitsu Y, Miyake C, Asada K, Muto S.

Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya, 464-8601 Japan.

In the previous paper [Kawano et al. (2000a) Plant Cell Physiol. 41: 1251], we demonstrated that addition of phenylethylamine (PEA) and benzylamine can induce an immediate and transient burst of active oxygen species (AOS) in tobacco suspension culture. Detected AOS include H2O2, superoxide anion and hydroxyl radicals. Use of several inhibitors suggested the presence of monoamine oxidase-like H2O2-generating activity in the cellular soluble fraction. It was also suggested that peroxidase(s) or copper amine oxidase(s) are involved in the extracellular superoxide production as a consequence of H2O2 production. Since more than 85% of the PEA-dependent AOS generating activity was localized in the extracellular space (extracellular fluid + cell wall), extracellularly secreted enzymes, probably peroxidases, may largely contribute to the oxidative burst induced by PEA. The PEA-induced AOS generation was also observed in the horseradish peroxidase (HRP) reaction mixture, supporting the hypothesis that peroxidases catalyze the oxidation of PEA leading to AOS generation. In addition to AOS production, we observed that PEA induced an increase in monodehydroascorbate radicals (MDA) in the cell suspension culture and in HRP reaction mixture using electron spin resonance spectroscopy and the newly invented MDA reductase-coupled method. Here we report that MDA production is an indicator of peroxidase-mediated generation of PEA radical species in tobacco suspension culture.