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L W Mapson

Publications and source records attributed to L W Mapson.

At least 19 recordsLinked to original sources
PubMed1970

A comparative study of the ability of methionine or linolenic acid to act as precursors of ethylene in plant tissues.

A comparative study has been made of the ability of three plant tissues to incorporate (14)C into ethylene from (14)C-labelled methionine and derivatives and from (14)C-labelled linolenic acid. Incorporation of label occurs readily from methionine and its derivative 4-methylmercapto-2-oxobutyric acid with apple, tomato or cauliflower floret tissue. No incorporation of label occurred, however, from uniformly (14)C-labelled linolenate.

Butyrates↗
PubMed1970

Stimulation by Erwinia carotovora of the synthesis of ethylene in cauliflower tissue.

The synthesis of ethylene by cauliflower floret tissue was increased when the tissue was inoculated with the soft-rot bacterium Erwinia carotovora. This effect was clearly associated with the production of pectic enzymes by the micro-organism. These enzymes, acting together with the plant enzymes, stimulated the production of ethylene from methionine. The increased synthetic activity was due to the release and increased activity of a glucose oxidase enzyme apparently attached to plant cell-wall material and liberated by the action of pectic enzymes of the bacterium.

Catalase↗
PubMed1969

Biosynthesis of ethylene. 4-methylmercapto-2-oxobutyric acid: an intermediate in the formation from methionine.

The enzyme responsible for the conversion of methionine into a precursor of ethylene in cauliflower florets is a transaminase. The formation of 4-methyl-mercapto-2-oxobutyric acid by this enzyme has been shown. The oxo acid stimulates the synthesis of ethylene when added to floret tissue, and tracer experiments have shown that (14)C is incorporated into ethylene from the labelled oxo acid. The evidence is consistent with the view that the oxo acid is an intermediate in the formation of ethylene from methionine.

Butyrates↗
PubMed1968

Biosynthesis of ethylene. Enzymes involved in its formation from methional.

1. Two enzymes were shown to be necessary for the production of ethylene from methional; they were separated from extracts of cauliflower florets by fractionation on Sephadex and other methods. 2. The first enzyme, generating hydrogen peroxide, appears to be similar to the fungal glucose oxidase, for like the latter it is highly specific for its substrate d-glucose. 3. The second enzyme, in the presence of cofactors and peroxide generated by the first enzyme, cleaves methional to ethylene. 4. It was also found that hydrogen peroxide in these reactions may be replaced by hydroperoxide generated from linolenic acid by lipoxidase enzymes. 5. Dihydroxyphenols were shown to have a marked inhibitory effect on these reactions and to account for the initial phase of low activity that is always observed in aqueous extracts prepared from the floret tissue.

Cellulose↗
PubMed1967

Biosynthesis of ethylene. Formation of ethylene from methional by a cell-free enzyme system from cauliflower florets.

1. The formation of ethylene from cauliflower florets is stimulated by the addition of either methionine or its hydroxy analogue. 2. Formation of ethylene from these compounds may also be demonstrated in cell-free extracts, but the most rapid formation is achieved by the addition of methional. 3. Fractionation of such extracts has shown that both particulate and non-particulate fractions are necessary for the formation of ethylene from methionine or its hydroxy analogues, but only the non-particulate fraction is necessary for its formation from methional. 4. A study of this system has shown that the conversion of methional into ethylene requires the presence of two enzyme systems, the first generating peroxide and the second catalysing the conversion of methional into ethylene in the presence of peroxide. 5. The presence of a heat-stable factor in cauliflower extracts that is necessary for the full activity of the enzyme converting methional into ethylene has also been shown. 6. The nature of this factor is at the present unknown; it is not a metal nor is it identifiable with many of the known coenzymes.

Aldehydes↗