The Role of Peroxidase in Ethylene Formation from 1-Aminocyclopropane-1-carboxylic Acid

Abstract

Summary Activity of ethylene formation from 1-aminocyclopropane-1-carboxylic acid (ACC) was compared to peroxidase (POD) activity in crude extracts of etiolated pea shoots ( Pisum sativum L.) as well as in Sephadex and Concanavalin A-Sepharose (ConA) fractions of these extracts. In crude extracts the stability of POD activity was higher than that of ethylene formation. Mercaptoethanol and sodiumazide inhibited both activities, but other inhibitors of ethylene formation (hydroxylammoniumchloride, catalase, EDTA, KCN, CuSO 4 , CoCl 2 ) had a weak or no effect at all on POD activity. High-molecular weight fractions (FI) from Sephadex of pea crude extracts formed ethylene from ACC and exhibited POD activity. By mixing high molecular weight fractions with low molecular weight fractions from the Sephadex column ethylene formation was stimulated. A similar effect could be reached by substituting FI fractions with horse radish peroxidase (HRP), but ethylene production was very low. After ConA fractionation the highest ethylene formation was found to be in the POD containing eluate, but in addition we found ethylene formation in effluent fractions which showed no POD activity. Mn 2+ otherwise has a stimulating effect on ethylene production from Sephadex fractions as well as from HRP but not on the crude extract. It appears that peroxidase itself does not play a major role in decarboxylation or ring cleavage of ACC, but that it might be involved in a more complex way by providing radicals, H 2 O 2 or otherwise unknown factors.