Quantitative Analysis of Pathways of Methionine Metabolism and Their Regulation in Lemna

Individual rates of metabolism of the sulfur, methyl, and 4-carbon moieties of methionine were estimated in Lemna paucicostata Hegelm. 6746 growing under standard conditions, and used to quantitate pathways of methionine metabolism. Synthesis of 5-adenosylmethionine (AdoMet) is the major pathway for...

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Bibliographic Details
Published in:Plant physiology (Bethesda) 1985-07, Vol.78 (3), p.555-560
Main Authors: Giovanelli, John, Mudd, S. Harvey, Anne H. Datko
Format: Article
Language:English
Subjects:
Adenine nucleotides
Biochemical pathways
Biological and medical sciences
Biosynthesis
Fundamental and applied biological sciences. Psychology
Metabolism
Metabolism. Physicochemical requirements
Phosphatidylcholines
Plant physiology and development
Plants
Protein metabolism
Radioactive decay
Radiocarbon
Solvents
Sulfur
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Summary:Individual rates of metabolism of the sulfur, methyl, and 4-carbon moieties of methionine were estimated in Lemna paucicostata Hegelm. 6746 growing under standard conditions, and used to quantitate pathways of methionine metabolism. Synthesis of 5-adenosylmethionine (AdoMet) is the major pathway for methionine metabolism, with over 4 times as much methionine metabolized by this route as accumulates in protein. More than 90% of AdoMet is used for transmethylation. Methyl groups of choline, phosphatidylcholine, and phosphorylcholine are major end products of this pathway. Flux through methylthio recycling is about one-third the amount of methionine accumulating in protein. Spermidine synthesis accounts for at least 60% of the flux through methylthio recycling. The results obtained here, together with those reported for methionine-supplemented plants (Giovanelli, Mudd, Datko 1981 Biochem Biophys Res Commun 100: 831-839), indicate that methionine supplementation reduced methylneogenesis by no more than the small amount expected from the reduced entry of sulfate sulfur into methionine (Giovanelli, Mudd, Datko, 1985 Plant Physiol 77: 450-455). Methionine supplementation had no significant effect on transmethylation or methylthio recycling. The combined data provide the first comprehensive estimates of the quantitative relationships of major pathways for methionine metabolism and their control in plants.
ISSN:0032-0889
1532-2548
DOI:10.1104/pp.78.3.555