Evaluation of the role of methional, 2-keto-4-methylthiobutyric acid and peroxidase in ethylene formation by Escherichia coli.
During growth of Escherichia coli strain SPA O in the presence of methionine, an intermediate accumulates in the medium. This intermediate reacts with 2,4-dinitrophenylhydrazine, and can be degraded to ethylene either enzymically or photochemically, the latter being stimulated by the addition of a flavin. The pH optimum for the photochemical degradation of this intermediate and 2-keto-4-methylthiobutyric acid (KMBA) is pH 3 whereas the optimum for methional is pH 6. The enzyme which converts the intermediate to ethylene also converts KMBA to ethylene and has many of the properties of a peroxidase including inhibition by catalase, cyanide, azide and anaerobiosis. The enzyme which synthesizes the intermediate is not known but requires oxygen and pyridoxal phosphate. A pathway for ethylene biosynthesis is proposed in which methionine is converted to KMBA which can be degraded either by peroxidase or in a flavin-mediated photochemical reaction. Its relevance to the properties of other ethylene-producing bacteria and to the proposed pathway of ethylene release by higher plants is discussed.
D000332:Aerobiosis; D003470:Culture Media; D004926:Escherichia coli / Q000378:metabolism*; D005030:Ethylenes / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008715:Methionine / Q000378:metabolism / Q000031:analogs & derivatives; D010544:Peroxidases / Q000378:metabolism
D003470:Culture Media; D005030:Ethylenes; C014632:2-keto-4-methylthiobutyric acid; D008715:Methionine; D010544:Peroxidases