Enzymology of l-tyrosine biosynthesis in corn (zea ma ys)

Byng, Graham S.; Whitaker, Robert J.; Flick, Christopher E.; Jensen, Roy A.

doi:10.1016/0031-9422(81)80023-4

Cited by 43 publications

(27 citation statements)

References 14 publications

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“…In the present work, only one peak of chorismate mutase activity was observed after DEAE cellulose chromatography of the extracts from Z. mays ( Fig. 2A) which is in agreement with a previous report (3). Similar contradictory results were obtained for Nicotiana tabacum by Goers and Jensen (14) who argued that the third isoenzyme reported earlier (27) may prove to be an electrophoretic variant of one of the four allelic CM-1 cistrons of N. tabacum.…”

Section: Methodssupporting

confidence: 62%

Chorismate Mutase Isoenzymes from Selected Plants and Their Immunological Comparison with the Isoenzymes from Sorghum bicolor

Singh¹,

Lonergan²,

Conn³

1986

Plant Physiol.

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The isoenzyme pattern of chorismate mutase (EC 5.4.99.5) was examined by diethylaminoethyl-cellulose chromatography in a wide variety of plants. All plants contained a regulated form of chorismate mutase (CM-I), and most contained an additional, unregulated form (CM-2). The regulatory properties of CM-I differed significantly between plants. Antisera prepared against CM-I and CM-2 from Sorghum bicolor were used to test immunological cross reaction of chorismate mutases from other plants. There was a high degree of similarity between chorismate mutase isoenzymes from Sorghum bicolor and Zea mays and some with Hordeum vulgare, but all other species studied were antigenically distinct from sorghum. No homology between the structure of CM-I and CM-2 was detected within any species.The shikimate pathway provides the precursors for the biosynthesis of the aromatic amino acids phenylalanine, tyrosine, and tryptophan in plants as well as in microorganisms (8,12,19 (15).In spite of the importance of chorismate mutase in phenylalanine and tyrosine biosynthesis, the information available in the literature is limited to a very few species. In this report, we present the partial purification, the regulatory properties and antigenic similarity to the sorghum enzyme of chorismate mutases from several species, differing in morphology (monocots and dicots) and physiology (C3, C4, and CAM). MATERIALS AND METHODSPlant Material. The plants used for this study were selected on the basis of their morphological and physiological characteristics. Green seedlings of Avena sativa (C3, monocot), Brassica oleracea (C3, dicot), Hordeum vulgare (C3, monocot), Pennisetum typhoides (C4, monocot), and Zea mays (C4, monocot) were grown by planting seeds in wet vermiculite in a growth chamber at 28°C under 12 h fluorescent illumination. Shoots from 6-to 7-d-old seedlings were used for the extraction of enzyme. Young, green leaves of Amaranthus hypochondriacus (C4, dicot), Hoya carnosa (CAM, dicot), Medicago sativa (C3, dicot), and Xerosicyos danguyi (CAM, dicot) were obtained from adult plants grown in a greenhouse and exposed to normal spring and summer daylengths. Young, green leaves from wild adult plants of Eschscholtzia californica (C3, dicot) were used. Spinacia oleracea (C3, dicot) leaves were obtained from a local supermarket.Enzyme Extraction. For the extraction of chorismate mutase, 20 to 25 g of shoots or leaf tissues were powdered in liquid N2 and extracted at 0 to 4°C with one volume of buffer A (100 mM Tris-HCl, pH 8.0, containing 1 mM tryptophan and 0.1% 2-mercaptoethanol). The extract was filtered through two layers of cheesecloth (grade 60) and centrifuged at 60,000g for 90 min in a Beckman model L ultracentrifuge. All subsequent purification steps were carried out at 0 to 4°C. Desalting. The centrifuged supernatant was loaded at 7 ml/min onto a bed of Sephadex G-25 (2.5 x 29.0 717 www.plantphysiol.org on April 1, 2019 -Published by Downloaded from

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Section: Methodssupporting

confidence: 62%

Chorismate Mutase Isoenzymes from Selected Plants and Their Immunological Comparison with the Isoenzymes from Sorghum bicolor

Singh¹,

Lonergan²,

Conn³

1986

Plant Physiol.

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“…It is possible that other plant systems may possess only a single glyphosate-sensitive DAHP synthase, in which case this enzyme may be the prime target of herbicidal action. (6,27), and are here reported to be glyphosate-insensitive for the first time in any system.…”

Section: Resultsmentioning

confidence: 61%

“…Data suggesting diversity in plant material as well (e.g. corn [6], mung bean [271, and tobacco [unpublished data]) are now coming to light. Second, the particular details of reversal of glyphosate inhibition by aromatic acids are variable from organism to organism.…”

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confidence: 99%

Enzymological Basis for Herbicidal Action of Glyphosate

Rubin¹,

Gaines²,

Jensen³

1982

Plant Physiol.

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The effects of 1 milliolar glyphosate (N-Iphosphonomethyllglycine) upon the activities ofenzymes of aromatic amino acid biosynthesis, partially purified by ion-exchange chromatography from mung bean seedings (Vigna radiata IL.I Wilczek), were examined. Multiple isozyme species of shikimate dehydrogenase, chorismate mutase, and aromatic aminotransferase were separated, and these were all insensitive to inhibition by glyphosate. [271, and tobacco [unpublished data]) are now coming to light. Second, the particular details of reversal of glyphosate inhibition by aromatic acids are variable from organism to organism. In E. coli, all three aromatic amino acids are required for complete reversal (25). In Rhizobium japonicum, the combination of phenylalanine plus tyrosine reversed glyphosate inhibition (18) in contrast to Lemna gibba where phenylalanine alone was adequate for reversal (18). In Euglena gracilis, aromatic amino acids only partially reverse inhibition (40%o) unless the minor pathway products: 4-aminobenzoate, 4-hydroxybenzoate, 2,3-dihydroxybenzoate, and 3,4-dihydroxybenzaldehyde are also present (5).Where partial reversal of inhibition is obtained with either Lphenylalanine alone or L-tyrosine alone, the greatest reversal is usually accomplished by L-phenylalanine. For example, the antagonism of inhibition by L-phenylalanine and L-tyrosine was 41% and 12% in Escherichia coli, and 27% and 3% in Chlamydomonas reinhardii (15). Qualitatively, it was found that L-phenylalanine was a better partial antagonist of glyphosate than L-tyrosine in suspension cultures of both carrot and soybean (15)

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“…Chloroplastic TYRA activity was previously reported (Byng et al, 1981;Siehl et al, 1986); however, none of these studies examined its possible presence within the cytosol. Sequence comparison with the Synechocystis enzyme (accession no.…”

Section: Analysis Of the Subcellular Localization Of The Two Tyrasmentioning

confidence: 98%

Tyrosine and Phenylalanine Are Synthesized within the Plastids in Arabidopsis

et al. 2009

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While the presence of a complete shikimate pathway within plant plastids is definitively established, the existence of a cytosolic postchorismate portion of the pathway is still debated. This question is alimented by the presence of a chorismate mutase (CM) within the cytosol. Until now, the only known destiny of prephenate, the product of CM, is incorporation into tyrosine (Tyr) and/or phenylalanine (Phe). Therefore, the presence of a cytosolic CM suggests that enzymes involved downstream of CM in Tyr or Phe biosynthesis could be present within the cytosol of plant cells. It was thus of particular interest to clarify the subcellular localization of arogenate dehydrogenases (TYRAs) and arogenate dehydratases (ADTs), which catalyze the ultimate steps in Tyr and Phe biosynthesis, respectively. The aim of this study was to address this question in Arabidopsis (Arabidopsis thaliana) by analysis of the subcellular localization of the two TYRAAts and the six AtADTs. This article excludes the occurrence of a spliced TYRAAt1 transcript encoding a cytosolic TYRA protein. Transient expression analyses of TYRA-and ADT-green fluorescent protein fusions reveal that the two Arabidopsis TYRA proteins and the six ADT proteins are all targeted within the plastid. Accordingly, TYRA and ADT proteins were both immunodetected in the chloroplast soluble protein fraction (stroma) of Arabidopsis. No TYRA or ADT proteins were immunodetected in the cytosol of Arabidopsis cells. Taken together, all our data exclude the possibility of Tyr and/or Phe synthesis within the cytosol, at least in green leaves and Arabidopsis cultured cells.

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Enzymology of l-tyrosine biosynthesis in corn (zea ma ys)

Cited by 43 publications

References 14 publications

Chorismate Mutase Isoenzymes from Selected Plants and Their Immunological Comparison with the Isoenzymes from Sorghum bicolor

Chorismate Mutase Isoenzymes from Selected Plants and Their Immunological Comparison with the Isoenzymes from Sorghum bicolor

Enzymological Basis for Herbicidal Action of Glyphosate

Tyrosine and Phenylalanine Are Synthesized within the Plastids in Arabidopsis

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