H. Gardner, J. Newton
1987
Citations
0
Influential Citations
34
Citations
Journal
Phytochemistry
Abstract
Abstract Ethylene was formed from 1-aminocyclopropane-1-carboxylic acid (ACC) by a wholly defined system containing linoleic acid hydroperoxide (LOOH), Mn 2+ and pyridoxal 5′-phosphate (PP) at pH 8.0. Under these conditions, neither oxygen nor lipoxygenase was required for ethylene production. Each component of the reaction mixture has been implicated as a cofactor required for aerobic in vitro conversion of ACC to ethylene by various plant preparations. Inhibition of ethylene formation by the α-tocopherol analogue, 2,2,5,7,8-pentamethyl-6-hydroxychroman, implies that free radicals are involved in the reaction. Peroxy radicals of LOOH were demonstrated to form in parallel with ethylene. Although PP was required for ethylene formation, peroxy radicals formed equally well with or without PP. This result implies that either a PP-ACC Schiff base reacts with peroxy radicals, or that peroxy radicals act through a PP-Mn n+ complex. Since the known stereochemistry argued against the former possibility [Pirrung, M. (1986) Biochemistry 25 , 114], the latter is suggested. A possible mechanism is proposed involving oxidation of ACC by a PP-Mn 4+ LOO − complex formed via sequential oxidation of Mn 2+ by LOOH and peroxy radicals derived from LOOH.