Ethylene Biosynthesis in Soil: I. Method of Assay in Conversion of 1-aminocyclopropane-1-carboxylic Acid to Ethylene1
- W. T. Frankenberger and
- Patrick J. Phelan2
Ethylene (C2H4) is a common biologically active secondary metabolite produced by soil microorganisms which can have a tremendous potential impact on crop yield. Methionine (MET) has been shown to be the major substrate for C2H4 biosynthesis in higher plants and soil microorganisms. Although 1-aminocyclopropane-1-carboxylic acid (ACC) is an intermediate in the conversion of MET to C2H4 in plant tissues, the immediate precursor of C2H4 and its biosynthetic pathway in soils has yet to be established. The primary objective of this study is to develop a method of assay to characterize the microbial conversion of ACC to C2H4 in soil. Results showed that the rate of C2H4 released from soil was enhanced with increasing pH (up to pH 9.0). The reaction rates of this transformation approached zero-order kinetics when 9.9 mM ACC was added to soils. Under standard conditions, the accumulation of C2H4 was linear with time of incubation for at least 7 d. Maximum reaction rates in the conversion of ACC to C2H4 were observed at 50°C with enzyme denaturation occurring at 55°C. ACC derived-C2H4 production in soils was enhanced under highly oxidized conditions and severely inhibited under anaerobiosis. Among various pretreatments that affected the conversion of ACC to C2H4, toluene, CoCl, and oscillation enhanced C2H4 biosynthesis, whereas, DMSO, formaldehyde, EDTA, 2-mercaptoethanol, 2,4-dinitrophenol, NaF, KCN, KNO2, and KNO3 inhibited this reaction.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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