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
- DOE Contract Number:
- EY-76-C-02-1338
- OSTI ID:
- 5578923
- Journal Information:
- Plant Physiol.; (United States), Journal Name: Plant Physiol.; (United States) Vol. 63:3; ISSN PLPHA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
551000 -- Physiological Systems
59 BASIC BIOLOGICAL SCIENCES
ALKENES
AMINO ACIDS
ATP
BIOLOGICAL PATHWAYS
BIOSYNTHESIS
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
ELEMENTS
ENZYME ACTIVITY
ENZYMES
ETHYLENE
HYDROCARBONS
LIPOTROPIC FACTORS
METHIONINE
NUCLEOTIDES
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
OXIDATION
PLANTS
PRECURSOR
SELENIUM
SEMIMETALS
SUBSTRATES
SYNTHESIS
TRANSFERASES