Enzymic evolution of ethylene from methional by a pea seedling extract

Ku, Han; Yang, Shang Fa; Pratt, Harlan K.

doi:10.1016/0003-9861(67)90413-4

Cited by 30 publications

(7 citation statements)

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confidence: 77%

“…If this ethylene-synthesizing system functions in vivo, the growth regulatory activities of the peroxidative IAA-oxidase system may encompass those areas in which ethylene is involved as well as the growth phenomena associated with IAA. This additional regulatory role for peroxidases is supported by their association with in vitro ethylene synthesis in several studies (22,23,25).The micronutrient manganese has been implicated as a cofactor in both the IAA-destroying system (15,20,21) and the ethylene-synthesizing system (1, 39). High levels of substrate manganese resulting in high levels of tissue manganese reportedly increase both the peroxidase activity and the IAAoxidase activity in cotton (31, 35).…”

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confidence: 96%

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The Relationship of the Peroxidative Indoleacetic Acid Oxidase System to in Vivo Ethylene Synthesis in Cotton

Fowler

Morgan

1972

Plant Physiol.

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Since peroxidase and manganese have been implicated in both auxin destruction and ethylene production, the effect of auxins and high tissue levels of manganese on the peroxidative indoleacetic acid oxidase system and the internal level of ethylene was determined in cotton (Gossypium hirsutum L.cv. Watson GL-7). The highest level of manganese tested produced manganese toxicity symptoms, including necrotic lesions, accompanied by an increase in internal ethylene levels at about 15 days after treatment initiation. Statistically significant increases in indoleacetic acid oxidase and peroxidase activity were first observed 2 days later and were paralleled by tissue manganese levels above 7.4 milligrams per gram dry weight and internal ethylene levels of 0.77 microliters per liter air. Eight hours after application of 2,4-dichlorophenoxyacetic acid or indoleacetic acid, the internal levels of ethylene were increased to above 6.6 microliters per liter air in cotton plants, and levels of this magnitude were maintained for a 72-hour period of observation. Modification of peroxidase and indoleacetic acid oxidase activity in auxintreated plants definitely occurred well after the elevation of internal ethylene levels. While ethylene levels and indoleacetic acid oxidase activity were increased by both experimental approaches, the earlier appearance of increased ethylene indicates that the peroxidative indoleacetic acid oxidase system in cotton is not involved in ethylene synthesis or that this enzyme is not the rate-limiting factor when ethylene synthesis is increased. Ethylene, as well as auxin destruction, may be involved in some of the long term plant responses to toxic levels of manganese. The findings also suggest that auxin-induced ethylene may play a role in the elevation of peroxidase and indoleacetic acid oxidase activity eventually seen in extracts of plants treated with auxins. The data support the assumption that the enzymatic portion of the indoleacetic acid oxidase system in cotton is a peroxidase. Thimann's observation, sufficient evidence has been accumulated to define the major substance responsible for auxin activity as indole-3-acetic acid and to attribute the destruction of IAA within the plant, primarily, to a peroxidase-based enzyme system generally known as IAA-oxidase (11,15,20,28,34,37). By virtue of its role in limiting the supply of IAA within the plant, the IAA-oxidase system has been recognized as a plant growth regulatory mechanism.The potential role of the IAA-oxidase system as a plant growth regulatory mechanism assumed new dimensions with Yang's (39) discovery that an enzyme system strikingly similar to the peroxidative IAA-oxidase system is capable of synthesizing the plant hormone ethylene. If this ethylene-synthesizing system functions in vivo, the growth regulatory activities of the peroxidative IAA-oxidase system may encompass those areas in which ethylene is involved as well as the growth phenomena associated with IAA. This additional regulatory role for peroxidases is supported...

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confidence: 77%

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The Relationship of the Peroxidative Indoleacetic Acid Oxidase System to in Vivo Ethylene Synthesis in Cotton

Fowler

Morgan

1972

Plant Physiol.

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“…This theory is based primarily upon the finding that inhibitors of protein and RNA synthesis prevent auxininduced ethylene production, and also on the observation that stimulation of ethylene production by auxin has a substantial lag period (1,5,7,18,19). Extracts of pea seedlings contain an enzyme that converts methional to ethylene in a cell-free system (20). The enzyme has been identified as a peroxidase (30), a protein which also catalyzes a number of other reactions including oxidation of IAA (13,14,26).…”

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“…Sections of subapical internodes or plumular hooks were homogenized in 50 mm potassium phosphate buffer at pH 7.8 (10 sections/ml), strained through cheesecloth, and centrifuged at lOOOg for 15 min. The preparation could be further purified by dialysis and ammonium sulfate precipitation as described by Ku et al. for the pea enzyme (20), but a variable loss in activity occurred at each step, making the crude extract preferable for quantitative studies. The resulting supernatant (enzyme preparation) was assayed in 5 ml of reaction mixture described by Yang (30), consisting of 10 mM potassium phosphate buffer (pH 7.8), 0.6 mm methional, 3 em manganese sulfate, 80 mm resorcinol, 2 ytM ethylenediaminetetraacetic acid, 80 fM sodium hydrogen sulfite, with 1 ml of enzyme extract.…”

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Mechanism of Auxin-induced Ethylene Production

1971

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Indoleacetic acid-induced ethylene production and growth in excised segments of etiolated pea shoots (Pisum sativum L. var. Alaska) parallels the free indoleacetic acid level in the tissue which in turn depends upon the rate of indoleacetic acid conjugation and decarboxylation. Both ethylene synthesis and growth require the presence of more than a threshold level of free endogenous indoleacetic acid, but in etiolated tissue the rate of ethylene production saturates at a high concentration and the rate of growth at a lower concentration of indoleacetic acid. Auxin stimulation of ethylene synthesis is not mediated by induction of peroxidase; to the contrary, the products of the auxin action which induce growth and ethylene synthesis are highly labile.It has been suggested that auxin may stimulate ethylene production by inducing the enzymes involved in the formation of the gas (1). This theory is based primarily upon the finding that inhibitors of protein and RNA synthesis prevent auxininduced ethylene production, and also on the observation that stimulation of ethylene production by auxin has a substantial lag period (1,5,7,18,19). Extracts of pea seedlings contain an enzyme that converts methional to ethylene in a cell-free system (20). The enzyme has been identified as a peroxidase (30), a protein which also catalyzes a number of other reactions including oxidation of IAA (13,14,26). The present study presents evidence which shows the peroxidase content not to play a role in the regulation of ethylene biosynthesis in pea seedlings. Growth, ethylene production, the endogenous IAA content, exogenous IAA level, and rate of metabolism of growth hormone were continuously determined and compared in an attempt to determine the mechanism by which auxin induces ethylene production. (29) which is approximately 100% efficient. The radioactivity remaining in the tissue after alcohol extraction was determined after squashing the sections and drying them on a planchet, under which condition self-absorption was negligible. Enzyme Assay for Ethylene Synthesis. Sections of subapical internodes or plumular hooks were homogenized in 50 mm potassium phosphate buffer at pH 7.8 (10 sections/ml), strained through cheesecloth, and centrifuged at lOOOg for 15 min. The preparation could be further purified by dialysis and ammonium sulfate precipitation as described by Ku et al. for the pea enzyme (20), but a variable loss in activity occurred at each step, making the crude extract preferable for quantitative studies. The resulting supernatant (enzyme preparation) was assayed in 5 ml of reaction mixture described by Yang (30), consisting of 10 mM potassium phosphate buffer (pH 7.8), 0.6 mm methional, 3 em manganese sulfate, 80 mm resorcinol, 2 ytM ethylenediaminetetraacetic acid, 80 fM sodium hydrogen sulfite, with 1 ml of enzyme extract. The mixture was incubated at 25 C in a 25-ml Erlenmeyer flask sealed with a vaccine cap, and typically 1-ml samples of air were withdrawn from the flask at 30-min intervals, and ethylene was ...

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“…In the FMN-light mediated model system (19), it has been established that methionine is converted to ethylene via methional (,a-methylthiopropionaldehyde) as an intermediate. Enzymic conversion of methionine analogs to ethylene catalvzed by peroxidase has been elucidated recently (5,6,11,12,15,17); a-keto-y-methylthiobutyric acid and methional, but not methionine, are the active substrates. A chemical mechanism accounting for suich enzymic formation of ethylene has been described (15)(16)(17)(18).…”

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confidence: 99%