Some Characteristics of the System Converting 1-Aminocyclopropane-1-carboxylic Acid to Ethylene

Self Cite

203

Ethylene production in apple fruit and protoplasts and in leaf tissue was inhibited by spermidine or spermine. These (15) during dark-induced senescence of detached leaves. Also, polyamines inhibit development of RNase and protease activity in barley leaf discs (15). The mechanism by which polyamines exert these effects is unknown. These effects, however, are the opposite of those caused by the plant growth regulator, ethylene, which promotes senescence of many plant tissues (8).We investigated the effect of polyamines on ethylene biosynthesis, partly because polyamines and ethylene derive from the same precursor, S-adenosylmethionine (1, 2, 16), and because of the possibility that polyamines regulate plant metabolism by influencing the biosynthesis of ethylene.

Section: Discussioncontrasting

confidence: 54%

Section: Discussionmentioning

confidence: 99%

Polyamines Inhibit Biosynthesis of Ethylene in Higher Plant Tissue and Fruit Protoplasts

Apelbaum¹,

Burgoon²,

Anderson³

et al. 1981

Self Cite

203

“…In 1981, Apelbaum et al (4) reported that apple discs convert 75,1984 C2H4 as well as CO2 (1). Thus, CO2 could act through a mass action effect in the inhibition of this reaction.…”

Section: Discussionmentioning

confidence: 99%

Effect of a Brief CO₂ Exposure on Ethylene Production

Chaves¹,

Tomás²

1984

Ethylene production and respiration by Granny Smith apples were inhibited by treatment with 20% CO2 for 2 hours. A similar effect was observed in tissue slices when treated at either 0 or 25°C.The inhibition continued even after an extended aeration period. There is also an inhibition of ethylene emission in tissue slices incubated with exogenous 1-aminocyclopropane-lI-crboxylc acid (ACC).In general, CO2 treatment increased the ACC content of the tissue. These observations are consistent with the idea the action of CO2 is directed toward the enzyme system responsible for the conversion of ACC into ethylene.The storage life of apples can be increased by treating the fruit with a high concentration of CO2 during a short period.Burg and Burg (9, 10) found that CO2 is a competitive inhibitor of ethylene action, and Beyer (5, 6) reported that such an action is related with ethylene metabolism. CO2 can affect this metabolism by inhibiting ethylene oxidation to CO2.The action of CO2 in delaying ripening rate has been related to a decrease in respiratory activity and an inhibition of the succinic oxidase complex and especially of the succinic dehydrogenase (18)(19)(20).In addition to its respiration blocking action, CO2 at high concentrations also decreases ethylene production in many fruits including apples, pears, tomatoes, etc. (7,8,(14)(15)(16) 22 phosphate buffer (pH 6.8), and 50 ug/ml chloramphenicol (4).In some experiments a HCO -CO2 buffer was used to control the CO2 concentration of the gas phase (21). The experiments were carried out with 10, 20, and 30% of CO2 at 0 and 25C.Experiments with Exogenous ACC. In some cases, ACC at 4 and 100 ;M was added to the incubation media. The experiments were carried out at 0 and 25C. Ethylene Determination. Ethylene production from whole fruit was measured by GC using a flame ionization detector. Samples were taken at the exit of the flushing gas stream as well as in the inner part of the fruit. A glass tube closed at one end with a septum was inserted into the apple core through its open end for internal ethylene sampling. CO2 Determination. CO2 was measured with a thermal conductivity detector GC fitted with a silica gel and molecular sieve columns.ACC Determination. Once the experiment was over, the tissue slices were removed from the incubation solution, washed and ACC extracted with 80% ethanol. After evaporation, the residue was taken up into water and ACC determined by the method of Lizada and Yang (13).Statistical Analysis. All experiments were repeated at least three times. The effects of CO2 treatment were evaluated by analysis of variance and the least significant differences between means (LSD) at the 0.05 level were calculated. RESULTSWhen whole fruits were treated with 20% CO2 for either 2 h or 5 d, ethylene production was inhibited. An initial 2-h exposure to 20% CO2 inhibited internal ethylene production by 28.4% after 5 d, whereas a continuous exposure to 20% CO2 inhibited ethylene production by 80% after the same 5-d period.Differences were larger...

“…recently reported an enzymic conversion of ACC to ethylene by a pea seedling extract, some characteristics of their system appear to us not to resemble the natural system. Based on in vivo observations, it is shown that EFE is present widely in plant tissues (1,3,6,7,9,14,17,24), requires 02 in the conversion (1), and is inhibited by high temperature (23), uncouplers of oxidative phosphorylation (23), Co2, (24), and osmotic shock (3). ACC is also known to be readily converted to ethylene nonenzymically by various chemicals (4, 13).…”

mentioning

confidence: 99%

Stereospecific Conversion of 1-Aminocyclopropanecarboxylic Acid to Ethylene by Plant Tissues

Hoffman¹,

Yang²,

ICHIHARA³

et al. 1982

121

Inasmuch as the molecule of 1-aminocyclopropanecarboxylic acid (ACC) possesses reflective symmetry but lacks rotational symmetry, the two chemically alike methylene groups can be distinguished by a stereospecific enzyme. To determine whether ACC conversion to ethylene by plant tissues proceeds in a stereospecific fashion, the four stereoisomers of 1-amino-2-ethylcyclopropanecarboxylic acid (AEC) were administered to postclimacteric apple (Malus sylvestris Mill., var. Golden Delicious), excised preclimacteric cantaloupe (Cucumis melo L., var. reticulatis Naud cv. PMR45), and etiolated mung bean ( Vigna radiata L., Wilczek, var. Berken) hypocotyls. In each case (lR,2S)-AEC was the preferred substrate yielding 1-butene. In contrast, all AEC isomers were converted equally well to butene by chemical oxidation using NaOCI. Both ACC and AEC appear to be substrates for the same enzyme since both reactions are inhibited in parallel by N2 or Co2+, both reactions are induced in parallel by excision, and when both substrates are present simultaneously each will act as an inhibitor with respect to the other. The aforementioned observations indicate that ACC is stereospecifically converted to ethylene. For AEC to be the most active precursor of 1-butene, the ethyl substituent should be trans to the carboxyl group and the pro-(S) methylene group should be unsubstituted. This observation leads to the suggestion that the enzyme interacts with amino, carboxyl, and pro-(S) methylene groups, a configuration corresponding to a L-amino acid. This view is consistent with the observation that the L-forms of alanine and methionine inhibit the conversion of ACC to ethylene more than the corresponding 1-amino acids in the mung bean hypocotyl system. recently reported an enzymic conversion of ACC to ethylene by a pea seedling extract, some characteristics of their system appear to us not to resemble the natural system. Based on in vivo observations, it is shown that EFE is present widely in plant tissues (1,3,6,7,9,14,17,24), requires 02 in the conversion (1), and is inhibited by high temperature (23), uncouplers of oxidative phosphorylation (23), Co2, (24), and osmotic shock (3). ACC is also known to be readily converted to ethylene nonenzymically by various chemicals (4, 13). This leads to the question of whether the conversion of ACC to ethylene by plant tissues is mediated by a nonenzymic chemical reaction.The ACC molecule contains two methylene groups and possesses reflective symmetry but lacks rotational symmetry. Consequently, the two chemically alike methylene groups can be distinguished by a stereospecific enzyme. Ethyl substitution of each of the four methylene hydrogens of ACC results in four stereoisomers of AEC whose absolute configurations are: (1 R, 2R), (1S, 2S), (IR, 2S), and (1S, 2R) (10, 11). (IS, 2S)-AEC has recently been identified as a hydrolysis product of coronatine, which is a toxin produced by a bacteria, Pseudomonas coronafaciens var. atropurpurea, and induces chlorosis in Italian ryegrass (15). Using the...