Some Characteristics of the System Converting 1-Aminocyclopropane-1-carboxylic Acid to Ethylene

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Abstract
The rate of C2H4 production in plant tissue appears to be limited by the level of endogenous 1-aminocyclopropane-1-carboxylic acid (ACC). Exogenous ACC stimulated C2H4 production considerably in plant tissues, but this required 10 to 100 times the endogenous concentrations of ACC before significant increases in C2H4 production were observed. This was partially due to poor penetration of ACC into the tissues. Conversion of ACC to C2H4 was inhibited by free radical scavengers, reducing agents, and copper chelators, but not by inhibitors of pyridoxal phosphate-mediated reactions. The system for converting ACC to C2H4 may be membrane-associated, for it did not survive treatment with surface-active agents and cold or osmotic shock reduced the capacity of the system to convert ACC to C2H4. The reaction rate was sensitive to temperatures above 29 and below 12 C, which suggests that the system may be associated with membrane-bound lipoproteins. The data presented support the possibility that the conversion of exogenous ACC to C2H4 proceeds via the natural physiological pathway.