'Blanquilla' Pear ACC Oxidase. Effect of CO(2) on In Vivo Activity

High levels of carbon dioxide have been used to prolong the storage life of fruits and vegetables because they reduce ethylene biosynthesis and perception. The precise mode Of CO(2) action is still not fully understood. ACC oxidase, the last enzyme in the ethylene biosynthesis pathwway, has been pointed to as a possible action site. In this study, the effect Of CO(2) on in vivo ACC oxidase activity in 'Blanquilla' pear (Pyrus communis) was investigated. We report experiments where CO(2) reduces, promotes or has no effect on in vivo ACC oxidase activity. The enzyme is differentially affected by CO(2) depending on the applied gas concentration, ripening stage of the tissue and on the conditions in which the activity is assayed. This study also shows that pH plays a key role in the regulation of CC oxidase activity by CO(2).