Subcellular localization of 1-aminocyclopropane-1-carboxylic acid oxidase in apple fruit.
1-Aminocyclopropane-1-carboxylic acid (ACC) oxidase catalyzes the oxidation of ACC to the gaseous plant hormone, ethylene. Although the enzyme does not contain a typical N-terminal consensus sequence for the transportation across the endoplasmic reticulum (ER), it has recently been shown to locate extracellularly by immunolocalization study. It was of interest to examine whether the enzyme contains a signal peptide that is overlooked by structure prediction. We observed that the in vitro translated apple ACC oxidase was not co-processed or imported by the canine pancreatic rough microsomes, a system widely used to identify signal peptide for protein translocation across ER, suggesting that apple ACC oxidase does not contain a signal peptide for ER transport. A highly specific polyclonal antibody raised against the recombinant apple ACC oxidase was used to examine the subcellular localization of the enzyme in apple fruit (Malus domestica, var. Golden Delicious). The location of ACC oxidase appeared to be mainly in the cytosol of the apple fruit pericarp tissue as was demonstrated by electron microscopy using immunogold-labeled antibodies. The pre-immune serum or pre-climacteric fruit control gave essentially no positive signal. Based on these observations, we conclude that ACC oxidase is a cytosolic protein.
Chung
Mei-Chu
MC
Institute of Botany, Academia Sinica, Nankang, Taipei, Taiwan 11529, R.O.C.
Chou
Shu-Jen
SJ
Kuang
Lin-Yun
LY
Charng
Yee-Yung
YY
Yang
Shang Fa
SF
D000594:Amino Acid Oxidoreductases / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D000598:Amino Acids, Cyclic / Q000378:metabolism; D003600:Cytosol / Q000201:enzymology; D005030:Ethylenes / Q000378:metabolism; D005638:Fruit / Q000737:chemistry / Q000201:enzymology*; D015151:Immunoblotting; D027845:Malus / Q000737:chemistry / Q000201:enzymology*; D016253:Microscopy, Immunoelectron; D014176:Protein Biosynthesis; D015398:Signal Transduction
D000598:Amino Acids, Cyclic; D005030:Ethylenes; C023863:1-aminocyclopropane-1-carboxylic acid; C036216:ethylene; D000594:Amino Acid Oxidoreductases; C059460:1-aminocyclopropane-1-carboxylic acid oxidase