S-methylmethionine is both a substrate and an inactivator of 1-aminocyclopropane-1-carboxylate synthase |
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Authors: | Ko SaeHee Eliot Andrew C Kirsch Jack F |
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Institution: | Department of Chemistry, University of California, 239 A Hildebrand Hall 3206, Berkeley, CA 94720-3206, USA |
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Abstract: | S-methyl-l-methionine (SMM) is ubiquitous in the tissues of flowering plants, but its precise function remains unknown. It is both a substrate and an inhibitor of the pyridoxal 5′-phosphate-dependent enzyme 1-aminocyclopropane-1-carboxylate (ACC) synthase, due to its structural similarity to the natural substrate of this enzyme, S-adenosyl-l-methionine. In the reaction with ACC synthase, SMM can either be transaminated to yield 4-dimethylsulfonium-2-oxobutyrate; converted to α-ketobutyrate, ammonia, and dimethylsulfide; or inactivate the enzyme covalently after elimination of dimethylsulfide. These results suggest a previously unrecognized role for SMM in the regulation of ACC synthase activity in plants. |
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Keywords: | 1-aminocyclopropane-1-carboxylate synthase ACC S-Methylmethionine Pyridoxal phosphate Ethylene biosynthesis Vinylglycine |
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