Indole-3-acetic Acid and p-Hydroxyacetophenone Driven Ethylene Formation from 1-Aminocyclopropane-1-carboxylic Acid Catalyzed by Horseradish Peroxidase

An in vitro system is described in which ethylene formation from the amino acid, 1-aminocyclopropane- 1-carboxylic acid (ACC), is catalyzed by horseradish peroxidase (HRP) in the presence of Mn²⁺ and p-hydroxyacetophenone (pHAP) as cofactors. The monophenol can be substituted for by indole-3-acetic acid or indole-3-methanol. Oxidative ACC breakdown is accelerated at acidic pH whereas ethylene formation in the presence of IAA is stimulated by pHAP with a pH optimum at 7.8. ACC oxidation is inhibited by propylgallate and ascorbic acid by 100%, whereas OH scavengers such as mannitol or formate have no effect.