Oxidation of ethylene by cotyledon extracts from Vicia faba L. |
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Authors: | P G Smith M A Venis M A Hall |
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Institution: | (1) Department of Botany and Microbiology, University College of Wales, SY 23 3DA Aberystwyth, Dyfed;(2) Shell Research Laboratories, Shell Research Ltd., ME9 8AG Sittingbourne, Kent, UK;(3) Present address: East Malling Research Station, ME19 6BJ Maidstone, Kent, UK |
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Abstract: | Improved rates of ethylene oxidation by cell-free preparations from cotyledons of Vicia faba L. have been obtained using cryogenic storage techniques and by developing a method for the hydrolysis of ethylene oxide. Gel permeation chromatography showed that a low-molecular-size fraction was required for activity; accordingly, the kinetics of ethylene oxidation in the presence of this fraction were studied. Reduced pyridine nucleotides could substitute for the low-molecular-size fraction. Activity under a nitrogen atmosphere was 60% lower than in air. The need for reduced nicotinamide adenine dinucleotide phosphate (NADPH) and oxygen indicated that the enzyme might be a mixed-function oxidase. Using sufficient NADPH to approach saturation, the apparent Michaelis constant (K
m) for ethylene was 1.94±0.38 · 10-8 M (aqueous phase), and when ethylene was saturating, the K
m for NADPH was 3.7 · 10-5 M. Carbon monoxide was found to inhibit by competing with ethylene, and the inhibitor constant was 5.97 · 10-7 M in solution. In the presence of excess ethylene and NADPH, activity was highest in phosphate-buffered medium pH 7.9. The bulk of the activity was found in a microsomal fraction.Abbreviations Epps
N-2-hydroxyethylpiperazine-N-3-propane sulphinic acid
- Tris
2-amino-2-(hydroxymethyl)-1,3-porpanediol |
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Keywords: | Ethylene oxidation Oxidase (mixed function) Vicia (ethylene oxidation) |
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