Extraction and biochemical characterization of wound-induced ACC oxidase from Citrus peel

1-Aminocyclopropane-1-carboxylate (ACC) oxidase from flavedo tissue of mandarin fruit was extracted and its biochemical properties investigated. Enzyme activity was induced by wounding and exposure to light. In vitro ACC oxidase activity required the presence of Fe2+ and ascorbate and was enhanced by addition of NaHCO3 to the reaction mixture. The apparent K-m of ACC was estimated to be 175 mu M in 30 mM NaHCO3. Recovery of the activity was only possible after passing the crude extract through Sephadex. The fraction retained in the column was found to strongly reduce the activity of the enzyme. Hence, the presence of low molecular weight inhibitors in the crude extract of mandarin flavedo is implied. ACC oxidase activity from Citrus has two temperature maxima, at 35 degrees C and 45 degrees C, and is inhibited by sulfhydryl reagents, metal chelators, free radical scavengers and divalent cations. These results indicate that ACC oxidase activity recovered from wounded flavedo tissue resembles authentic in vivo activity and that the biochemical properties of the enzyme in a non-climacteric fruit are very similar to those observed in other climacteric-like tissues.