Apple fruit copper amine oxidase isoforms: peroxisomal MdAO1 prefers diamines as substrates, whereas extracellular MdAO2 exclusively utilizes monoamines

4-Aminobutyrate (GABA) accumulates in apple fruit during controlled atmosphere storage. A potential source of GABA is the polyamine putrescine, which can be oxidized via copper-containing amine oxidase (CuAO), resulting in the production 4-aminobutanal/Δ(1)-pyrroline, with the consumption of O2 and...

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Bibliographic Details
Published in:	Plant and cell physiology Vol. 56; no. 1; pp. 137 - 147
Main Authors:	Zarei, Adel, Trobacher, Christopher P, Cooke, Alison R, Meyers, Ashley J, Hall, J Christopher, Shelp, Barry J
Format:	Journal Article
Language:	English
Published:	Japan 01-01-2015
Subjects:	Allium cepa Amine Oxidase (Copper-Containing) - genetics Amine Oxidase (Copper-Containing) - metabolism Amino Acid Sequence Arabidopsis Arabidopsis - cytology Arabidopsis - enzymology Arabidopsis - genetics Biogenic Monoamines - metabolism Biosynthetic Pathways Diamines - metabolism Extracellular Space - enzymology Fruit - cytology Fruit - enzymology Fruit - genetics gamma-Aminobutyric Acid - metabolism Gene Expression Regulation, Plant Isoenzymes Malus - enzymology Malus - genetics Malus domestica Molecular Sequence Data Onions - cytology Onions - enzymology Onions - genetics Organ Specificity Oxidation-Reduction Peroxisomes - enzymology Plant Proteins - genetics Plant Proteins - metabolism Polyamines - metabolism Sequence Alignment Substrate Specificity Recombinant expression Abiotic stress 4-Aminobutyrate Subcellular localization Copper amine oxidase Apple fruit Enzyme kinetics Polyamines
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Summary:	4-Aminobutyrate (GABA) accumulates in apple fruit during controlled atmosphere storage. A potential source of GABA is the polyamine putrescine, which can be oxidized via copper-containing amine oxidase (CuAO), resulting in the production 4-aminobutanal/Δ(1)-pyrroline, with the consumption of O2 and release of H2O2 and ammonia. Five putative CuAO genes (MdAO genes) were cloned from apple (Malus domestica Borkh. cv. Empire) fruit, and the deduced amino acid sequences found to contain the active sites typically conserved in CuAOs. Genes encoding two of these enzymes, MdAO1 and MdAO2, were highly expressed in apple fruit and selected for further analysis. Amino acid sequence analysis predicted the presence of a C-terminal peroxisomal targeting signal 1 tripeptide in MdAO1 and an N-terminal signal peptide and N-glycosylation site in MdAO2. Transient expression of green fluorescent fusion proteins in Arabidopsis protoplasts or onion epidermal cells revealed a peroxisomal localization for MdAO1 and an extracellular localization for MdAO2. The enzymatic activities of purified recombinant MdAO1 and MdAO2 were measured continuously as H2O2 production using a coupled reaction. MdAO1 did not use monoamines or polyamines and displayed high catalytic efficiency for 1,3-diaminopropane, putrescine and cadaverine, whereas MdAO2 exclusively utilized aliphatic and aromatic monoamines, including 2-phenylethylamine and tyramine. Together, these results indicate that MdAO1 may contribute to GABA production via putrescine oxidation in the peroxisome of apple fruit under controlled atmosphere conditions. MdAO2 seems to be involved in deamination of 2-phenylethylamine, which is a step in the biosynthesis of 2-phenylethanol, a contributor to fruit flavor and flower fragrance.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0032-0781 1471-9053
DOI:	10.1093/pcp/pcu155