Effects of carbon dioxide on ethylene-forming enzyme in Japanese pear and apple

Abstract

Ethylene-forming enzyme (EFE) activity was stimulated by CO 2 in both of Hosui and Granny Smith fruit discs. In Hosui fruit, EFE activity remained unchanged up to 5% CO 2 , but increased with higher CO 2 levels. In Granny Smith fruit, EFE increased gradually as CO 2 increased from 5 to 30%. EFE developed with storage time at 1±1°C in both fruits. Treating discs with cycloheximide showed that CO 2 induced EFE biosynthesis in Granny Smith apple stored for a short time, but not in Hosui fruit. Kinetic data from the interaction of CO 2 and 1-aminocyclopropane-1-carboxylic acid (ACC) on EFE activity indicated that CO 2 increased the maximum reaction rate ( V max ) of EFE in discs of both fruit without changing the apparent Michaelis-Menton constant ( K m ) value. EFE activity in Hosui fruit discs was stimulated by CO 2 only when ACC was added exogenously. It is suggested that the stimulatory effect of CO 2 on EFE activity may be caused by a CO 2 -EFE-ACC or EFE-ACC-CO 2 complex which enhances the maximum reaction rate of conversion of ACC to ethylene.