Biosynthesis of Indoleacetic Acid from Tryptophan-<sup>14</sup>C in Cell-free Extracts of Pea Shoot Tips

Moore, Thomas C.; Shaner, Coralie A.

doi:10.1104/pp.42.12.1787

Cited by 18 publications

(7 citation statements)

References 36 publications

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“…Hayashi and Murakami (1953) first demonstrated that GA increases elongation growth of pea stem segments incubated in L-Trp. The finding that both tryptamine and IPyA induced elongation is in agreement with reports that both can act as precursors in pea, though the TAT pathway seems to be the only significant source of IAA in Pisum in vivo; Moore andShaner (1967, 1968) demonstrated that while both Trp and tryptamine were converted to IAA, Trp was not converted to tryptamine, implying that TDC is not an IAA biosynthetic enzyme, and another report showed that Trp decarboxylation is not specifically related to IAA synthesis (Reed 1968). Taken together, all of these results suggest that the conversion of L-Trp to IPyA is the rate-limiting step in IAA biosynthesis in this system.…”

Section: Growth Of Pea Stem Segmentssupporting

confidence: 92%

“…There are a number of reports in which D-Trp was at least as effective as L-Trp as an auxin precursor (discussed in Miura and Mills 1971). Many studies of the role of Trp as an IAA precursor used racemic mixtures of D-and L-Trp in feeding experiments or compared metabolism of labeled D-and L-Trp, in which levels of isomeric contamination exceeded the amounts of IAA formed (e.g., Kim and Rohringer 1969, Moore and Shaner 1967, 1968, Wightman and Cohen 1968. It now seems clear that care must be taken to ascertain isomeric purity and that the assumption that the D isomer is inert is not well founded.…”

Section: Ti-yptophan Stereoisomers and Iaa Biosynthesismentioning

confidence: 99%

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Gibberellin‐enhanced indole‐3‐acetic acid biosynthesis: D‐Tryptophan as the precursor of indole‐3‐acetic acid

Law

1987

Physiologia Plantarum

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Stem segments excised from light‐grown Pisum sativum L. (cv. Little Marvel) plants elongated in the presence of indole‐3‐acetic acid and its precursors, except for L‐tryptophan, which required the addition of gibberellin A, for induction of growth. Segment elongation was promoted by D‐tryptophan without a requirement for gibberellin, and growth in the presence of both D‐tryptophan and L‐tryptophan with gibberellin A3, was inhibited by the D‐aminotransferase inhibitor D‐cycloserine. Tryp‐tophan racemase activity was detected in apices and promoted conversion of L‐tryptophan to the D isomer; this activity was enhanced by gibberellin A3. When applied to apices of intact untreated plants, radiolabeled D‐tryptophan was converted to indole‐3‐acetic acid and indoleacetylaspartic acid much more readily than L‐tryptophan. Treatment of plants with gibberellin A3, 3 days prior to application of labeled tryptophan increased conversion of L‐tryptophan to the free auxin and its conjugate by more than 3‐fold, and led to labeling of N‐malonyl‐D‐tryptophan. It is proposed that gibberellin increases the biosynthesis of indole‐3‐acetic acid by regulating the conversion of L‐tryptophan to D‐tryptophan, which is then converted to the auxin.

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Section: Growth Of Pea Stem Segmentssupporting

confidence: 92%

Section: Ti-yptophan Stereoisomers and Iaa Biosynthesismentioning

confidence: 99%

Gibberellin‐enhanced indole‐3‐acetic acid biosynthesis: D‐Tryptophan as the precursor of indole‐3‐acetic acid

Law

1987

Physiologia Plantarum

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“…Particular attention was given to the formation of indolepyruvate from tryptophan via transamination because of the implication of that reaction in the biosynthesis of IAA in peas (20)(21)(22). The formation of equimolar yields of indolepyruvate and glutamate from tryptophan and a-ketoglutarate was readily demonstrable under anaerobic conditions, which prevented loss of indolepyruvate.…”

Section: Resultsmentioning

confidence: 99%

“…The purpose of these investigations was to purify partially and ascertain some properties of a transaminase fraction from pea shoots and to attempt to corroborate the evidence reported by Moore (20) and Moore and Shaner (21,22) Preparation of Enzyme Extract. Each sample of shoot tips was homogenized in a chilled mortar and pestle with 2 ml of 0.5 M borate buffer (pH 8.5), containing 150 ltM chloramphenicol and 1 mm dithiothreitol, per g fresh weight of tissue.…”

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confidence: 98%

Properties of an Aminotransferase of Pea (Pisum sativum L.)

Matheron¹,

Moore²

1973

Plant Physiol.

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A transaminase (aminotransferase, EC 2.6.1) fraction was partially purfied from shoot tips of pea (Pisum sativum L. cv. Transaminases (aminotransferases, EC 2.6. 1), particularly those of plants, are quite incompletely described in regard to their amino acid and keto acid specificities. Some partially purified preparations are highly specific for particular amino acids (1, 2, 5, 30). Other preparations reportedly transaminate a variety of amino acids (7,8,12,15,25,29). Many workers have concentrated on transamination of aromatic amino acids. Two transaminase fractions have been isolated from rat brain, one of which showed highest activity toward tyrosine and phenylalanine and the other of which showed highest activity toward tryptophan and 5-hydroxytryptophan (4, 6, 26). Partially purified tryptophan transaminase from the bacterium Clostridium sporogenes catalyzed the transamination of tyrosine and phenylalanine, as well as tryptophan (23). A transaminase fraction from mung bean (Phaseolus aureus) also transaminated tryptophan, phenylalanine, and tyrosine, as well as several aliphatic amino acids (7,8).The purpose of these investigations was to purify partially and ascertain some properties of a transaminase fraction from pea shoots and to attempt to corroborate the evidence reported by Moore (20) and kept under a 16-hr photoperiod at 20 + 1 C with a light intensity of 900 to 1000 ft-c and an 8-hr dark period at 16 + 1 C. After 10 to 14 days, 50 to 70 g of shoot tips were removed immediately above the fifth node and placed in liquid nitrogen for overnight storage prior to use.Preparation of Enzyme Extract. Each sample of shoot tips was homogenized in a chilled mortar and pestle with 2 ml of 0.5 M borate buffer (pH 8.5), containing 150 ltM chloramphenicol and 1 mm dithiothreitol, per g fresh weight of tissue. The homogenate then was centrifuged at 40,000g for 10 min at 4 C, and the resulting supernatant was the crude enzyme extract. The extract was then brought to 25% (v/v) acetone with the addition of ice-cold acetone. After setting in an ice bath for 10 min, the 25% (v/v) acetone-crude extract was centrifuged at 10,000g for 10 min. The supernatant was then brought to 60% (v/v) acetone, allowed to set for 10 min in an ice bath and then was centrifuged at 10,000g for 10 min. The resultant supernatant was discarded, and the pellet was resuspended in 0.5 M borate buffer (pH 8.5) in a total of one-sixth of the original volume of crude extract. This suspension was then centrifuged at 40,000g for 10 min, and the resulting goldyellow colored supernatant was used as the acetone-precipitated enzyme fraction. In some studies, the acetone-precipitated enzyme was added to a column of hydroxylapatite (1.6 x 17 cm) which was previously equilibrated with 0.02 M KH,PO4-Na2HPO, buffer at pH 8.5. The column was then washed with 70 ml of 0.05 M sodium-potassium phosphate buffer (pH 8.5) and 50 ml of 0.08 M sodium-potassium phosphate buffer (pH 8.5). The enzyme was then eluted with 0.15 M sodium-potassium phosphate buffer...

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“…The possibility that bacterial contamination could account for the auxin synthesis ascribed to plant tissues in recent reports (7,13) was dismissed for a number of reasons including the following: surface sterilization procedures were employed and were followed by a thorough washing of the tissue; high speed centrifugation techniques were used; a short time interval was used for the enzyme assays; and antibiotics were included in the reaction mixtures. (5).…”

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confidence: 99%

Invasion of Plant Tissue by Bacteria Under In Vitro Conditions

1968

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Biosynthesis of Indoleacetic Acid from Tryptophan-¹⁴C in Cell-free Extracts of Pea Shoot Tips

Cited by 18 publications

References 36 publications

Gibberellin‐enhanced indole‐3‐acetic acid biosynthesis: D‐Tryptophan as the precursor of indole‐3‐acetic acid

Gibberellin‐enhanced indole‐3‐acetic acid biosynthesis: D‐Tryptophan as the precursor of indole‐3‐acetic acid

Properties of an Aminotransferase of Pea (Pisum sativum L.)

Invasion of Plant Tissue by Bacteria Under In Vitro Conditions

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Biosynthesis of Indoleacetic Acid from Tryptophan-14C in Cell-free Extracts of Pea Shoot Tips

Cited by 18 publications

References 36 publications

Gibberellin‐enhanced indole‐3‐acetic acid biosynthesis: D‐Tryptophan as the precursor of indole‐3‐acetic acid

Gibberellin‐enhanced indole‐3‐acetic acid biosynthesis: D‐Tryptophan as the precursor of indole‐3‐acetic acid

Properties of an Aminotransferase of Pea (Pisum sativum L.)

Invasion of Plant Tissue by Bacteria Under In Vitro Conditions

Contact Info

Product

Resources

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Biosynthesis of Indoleacetic Acid from Tryptophan-¹⁴C in Cell-free Extracts of Pea Shoot Tips