Interactions of methionine and selenomethionine with methionine adenosyltransferase and ethylene-generating systems
Since selenomethionine appears to be a better precursor of ethylene in senescing flower tissue of Ipomoea tricolor and in indole acetic acid-treated pea stem sections than is methionine, we compared the effectiveness of selenomethionine and methionine to participate in reactions which may be connected to ethylene biosynthesis. Evidence is presented that selenomethionine is also a better substrate of methionine adenosyltransferase (ATP: methionine S-adenosyltransferase, EC 2.5.1.6) from I. tricolor, the V/sub max/ for selenomethionine being twice as high as that for methionine. The affinity of the enzyme is higher for methionine than for selenomethionine, however. Methionine added to flower tissue together with selenomethionine inhibits the enhancement of ethylene synthesis by the seleno analog. Likewise, methionine reduces the high, selenomethionine-dependent reaction rates of methionine adenosyltransferase from I. tricolor flower tissue. On the other hand, selenomethionine is less effective as an ethylene precursor than is methionine in model systems involving oxidation by free radicals. It was concluded that activation of methionine by methionine adenosyltransferase and formation of S-adenosylmethionine are more likely to be involved in ethylene biosynthesis than is oxidation of methionine by free radicals.
- Research Organization:
- Michigan State Univ., East Lansing, MI (United States)
- DOE Contract Number:
- EY-76-C-02-1338
- OSTI ID:
- 5578923
- Journal Information:
- Plant Physiol.; (United States), Vol. 63:3
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ETHYLENE
BIOSYNTHESIS
TRANSFERASES
ENZYME ACTIVITY
ATP
BIOLOGICAL PATHWAYS
METHIONINE
OXIDATION
PLANTS
PRECURSOR
SELENIUM
SUBSTRATES
ALKENES
AMINO ACIDS
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
ELEMENTS
ENZYMES
HYDROCARBONS
LIPOTROPIC FACTORS
NUCLEOTIDES
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
SEMIMETALS
SYNTHESIS
550200* - Biochemistry
551000 - Physiological Systems