Differentially Regulated Isozymes of 3-Deoxy-d-<i>arabino</i>-Heptulosonate-7-Phosphate Synthase from Seedlings of <i>Vigna radiata</i> [L.] Wilczek

Rubin, Judith L.; Jensen, Roy A.

doi:10.1104/pp.79.3.711

Cited by 75 publications

(51 citation statements)

References 26 publications

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“…This reflects different biochemical pathway steps diverging from prephenate in these organisms (36). The minor sensitivity of X. campestris AroA II to inhibition by L-tryptophan is paralleled by a similar sensitivity noted for plant AroA II in at least one case (mung bean) (26). AroA II from either source is quite labile and exhibits a relatively high temperature optimum.…”

Section: Discussionmentioning

confidence: 92%

Microbial Origin of Plant-Type 2-Keto-3-Deoxy- d - arabino -Heptulosonate 7-Phosphate Synthases, Exemplified by the Chorismate- and Tryptophan-Regulated Enzyme from Xanthomonas campestris

2001

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Enzymes performing the initial reaction of aromatic amino acid biosynthesis, 2-keto-3-deoxy-D-arabinoheptulosonate 7-phosphate (DAHP) synthases, exist as two distinct homology classes. The three classic Escherichia coli paralogs are AroA I proteins, but many members of the Bacteria possess the AroA II class of enzyme, sometimes in combination with AroA I proteins. AroA II DAHP synthases until now have been shown to be specifically dedicated to secondary metabolism (e.g., formation of ansamycin antibiotics or phenazine pigment). In contrast, here we show that the Xanthomonas campestris AroA II protein functions as the sole DAHP synthase supporting aromatic amino acid biosynthesis. X. campestris AroA II was cloned in E. coli by functional complementation, and genes corresponding to two possible translation starts were expressed. We developed a 1-day partial purification method (>99%) for the unstable protein. The recombinant AroA II protein was found to be subject to an allosteric pattern of sequential feedback inhibition in which chorismate is the prime allosteric effector. L-Tryptophan was found to be a minor feedback inhibitor. An N-terminal region of 111 amino acids may be located in the periplasm since a probable inner membrane-spanning region is predicted. Unlike chloroplast-localized AroA II of higher plants, X. campestris AroA II was not hysteretically activated by dithiols. Compared to plant AroA II proteins, differences in divalent metal activation were also observed. Phylogenetic tree analysis shows that AroA II originated within the Bacteria domain, and it seems probable that higher-plant plastids acquired AroA II from a gram-negative bacterium via endosymbiosis. The X. campestris AroA II protein is suggested to exemplify a case of analog displacement whereby an ancestral aroA I species was discarded, with the aroA II replacement providing an alternative pattern of allosteric control. Three subgroups of AroA II proteins can be recognized: a large, central group containing the plant enzymes and that from X. campestris, one defined by a three-residue deletion near the conserved KPRS motif, and one possessing a larger deletion further downstream.Microorganisms and plants engage 3-deoxy-D-arabino-heptulosonate 7-phosphate (DAHP) synthase (EC 4.1.2.15) as the initial catalyst for the commitment of phosphoenolpyruvate (PEP) and erythrose 4-phosphate (E4P) to the biosynthesis of aromatic amino acids, vitamin K, folic acid, and ubiquinone (4). The pathway contributes heavily to the biochemical individuality of organisms, with an enormous variety of peripheral branch connections known. Various pigments, siderophores, signaling compounds, defense metabolites, structural compounds, antibiotics, and other secondary metabolites are derived from this pathway (4).DAHP synthases fall into two distinct homology families. The AroA I family is divided into subfamilies AroA I␣ and AroA I␤ (32). The AroA I␣ subfamily is widely represented in gram-negative bacteria in which differentially regulated paralogs are commonly exp...

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Section: Discussionmentioning

confidence: 92%

Microbial Origin of Plant-Type 2-Keto-3-Deoxy- d - arabino -Heptulosonate 7-Phosphate Synthases, Exemplified by the Chorismate- and Tryptophan-Regulated Enzyme from Xanthomonas campestris

2001

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“…A highly active aminotransferase enzyme having an unusually narrow substrate specificity for prephenate exists in mung bean (3), tobacco (23), and sorghum (C. A. Bonner and R.A.J., unpublished data). L-Arogenate plays a role as a feedback inhibitor of 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase (DAHP synthase-Mn) in the chloroplast (24,25). This regulation would be maximally attractive (see later section) if L-arogenate accumulates as a consequence of feedback-inhibition of arogenate dehydrogenase and arogenate dehydratase.…”

Section: Resultsmentioning

confidence: 99%

Chloroplasts of higher plants synthesize L-phenylalanine via L-arogenate.

Jung¹,

Zamir²,

Jensen³

1986

Proc. Natl. Acad. Sci. U.S.A.

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The specific enzymological route of L-phenylalanine biosynthesis has not been established in any higher plant system. The possible pathway routes that have been identified in microorganisms utilize either phenylpyruvate or L-arogenate as a unique intermediate. We now report the presence ofarogenate dehydratase (which converts L-arogenate to L-phenylalanine) in cultured-cell populations of Nicotiana silvestris. Prephenate dehydratase (which converts prephenate to phenylpyruvate) was not detected. Arogenate dehydratase was also found in washed spinach chloroplasts, and these data add to emerging evidence in support of the existence in the plastidial compartment of a complete assembly of enzymes comprising aromatic amino acid biosynthesis. Arogenate dehydratase from tobacco and spinach were both specific for L-arogenate, inhibited by L-phenylalanine, and activated by L-tyrosine. Apparent K. values for L-arogenate (0.3 x 10-3 M), pH optima (pH 8.5-9.5), and temperature optima for catalysis (32-340C) were also similar.The current understanding of the post-prephenate pathways of phenylalanine and tyrosine biosynthesis and of their regulation has depended almost entirely upon a large base of comparative data from both prokaryotic and eukaryotic microorganisms (1). Until recently it had been assumed that higher plants utilize phenylpyruvate and 4-hydroxyphenylpyruvate as biosynthetic precursors of L-phenylalanine and L-tyrosine, respectively. A similar assumption prevailed for microorganisms until 1974, when enzymatic formation of L-arogenate from prephenate and enzymatic conversion of L-arogenate to L-tyrosine was first recognized in cyanobacteria (2). Since then, the arogenate pathway to L-tyrosine has been demonstrated in mung bean (3), corn (4), sorghum (5), tobacco (6), spinach (7), and buckwheat (J. L. Rubin and R.A.J., unpublished data). Prephenate dehydrogenase activity has not been found in any plant system, except in the developmental stage of seed germination in mung bean. Hence, the arogenate pathway appears to be the major, if not exclusive, mode of L-tyrosine biosynthesis in higher plants.Progress with the phenylalanine pathway has been slower, largely because ofthe technical difficulty ofthe enzyme assay (8,9). Fig. 1 (Binghamton, NY). The background and characteristics of the cell line ANS-1 of N.silvestris have been described (6). Suspension cultures of these cells were maintained by 1:4 dilution every 8 days into fresh medium. In this subculture routine, the cells undergo a lag phase of "'36 hr followed by a period of exponential growth that lasts until about day 6, when the cells enter a stationary phase.Cells were harvested in late-exponential phase between days 4 and 5 on Miracloth filters and were washed three times with 3% (wt/vol) mannitol. Excess wash solution was removed with the aid of a suction filter. The cell pack was frozen in liquid nitrogen and stored at -80'C or was ground in liquid nitrogen using a Waring blender and stored as a frozen powder at -80'C.Preparation of Partially...

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“…In microorganisms, arogenate, an intermediate compound formed after chorismate, can function as a physiologic regulator of DAHPS. However, arogenate does not accumulate in plants at detectable levels suggesting that regulation of DAHPS in plants occurs preferentially at genetic levels (Rubin & Jensen, 1985).…”

Section: Glyphosate Mode Of Actionmentioning

confidence: 99%

A Modified phosphate-carrier protein theory is proposed as a non-target site mechanism For glyphosate resistance in weeds

Roso

Vidal

2010

Planta daninha

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-Glyphosate is an herbicide that inhibits the enzyme 5-enolpyruvyl-shikimate-3-phosphate synthase (EPSPs) (EC 2.5.1.19). EPSPs is the sixth enzyme of the shikimate pathway, by which plants synthesize the aromatic amino acids phenylalanine, tyrosine, and tryptophan and many compounds used in secondary metabolism pathways. About fifteen years ago it was hypothesized that it was unlikely weeds would evolve resistance to this herbicide because of the limited degree of glyphosate metabolism observed in plants, the low resistance level attained to EPSPs gene overexpression, and because of the lower fitness in plants with an altered EPSPs enzyme. However, today 20 weed species have been described with glyphosate resistant biotypes that are found in all five continents of the world and exploit several different resistant mechanisms. The survival and adaptation of these glyphosate resistant weeds are related toresistance mechanisms that occur in plants selected through the intense selection pressure from repeated and exclusive use of glyphosate as the only control measure. In this paper the physiological, biochemical, and genetic basis of glyphosate resistance mechanisms in weed species are reviewed and a novel and innovative theory that integrates all the mechanisms of non-target site glyphosate resistance in plants is presented.Keywords: membrane carrier proteins, herbicide, weed resistance.RESUMO -Glyphosate é uma glicina fosfonada e inibe a enzima 5-enolpiruvil-shikimato-3-fosfato sintase (EPSPS) (EC 2.5.1.19). EPSPS é a sexta enzima da rota do shikimato, na qual são sintetizados os compostos do metabolismo secundário e os aminoácidos aromáticos fenilalanina, tirosina e triptofano. Alguns autores hipotetizaram que seria improvável a evolução de plantas daninhas resistentes a este herbicida. As justificativas estariam relacionadas à limitada metabolização de glyphosate nas plantas, ao baixo nível de resistência obtido com a superexpressão do gene EPSPS e à alta penalidade de adaptação oriunda de mutações no gene EPSPS. Mas, atualmente estão descritas 18 espécies com biótipos resistentes distribuídas em 17 países. A sobrevivência e adaptação estão relacionadas aos mecanismos de resistência que ocorrem nas plantas daninhas selecionadas em função da intensa pressão de seleção do herbicida. Esta revisão objetiva apresentar e discutir evidências fisiológicas, bioquímicas e genéticas que fundamentam os principais mecanismos envolvidos na resistência ao herbicida glyphosate em plantas daninhas.Palavras-chave: herbicida, proteínas carregadoras de membrana, planta daninha.

show abstract

Differentially Regulated Isozymes of 3-Deoxy-d-arabino-Heptulosonate-7-Phosphate Synthase from Seedlings of Vigna radiata [L.] Wilczek

Cited by 75 publications

References 26 publications

Microbial Origin of Plant-Type 2-Keto-3-Deoxy- d - arabino -Heptulosonate 7-Phosphate Synthases, Exemplified by the Chorismate- and Tryptophan-Regulated Enzyme from Xanthomonas campestris

Microbial Origin of Plant-Type 2-Keto-3-Deoxy- d - arabino -Heptulosonate 7-Phosphate Synthases, Exemplified by the Chorismate- and Tryptophan-Regulated Enzyme from Xanthomonas campestris

Chloroplasts of higher plants synthesize L-phenylalanine via L-arogenate.

A Modified phosphate-carrier protein theory is proposed as a non-target site mechanism For glyphosate resistance in weeds

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