The Two-Isozyme System of 3-Deoxy-d-<i>arabino</i>-Heptulosonate 7-Phosphate Synthase in <i>Nicotiana silvestris</i> and Other Higher Plants

Ganson, Robert J.; d'Amato, T. A.; Jensen, Roy A.

doi:10.1104/pp.82.1.203

Cited by 79 publications

(57 citation statements)

References 21 publications

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“…Other enzymes in the aromatic amino acid pathways, such as 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase, 5-enolpyruvylshikimate-3-phosphate synthase, and tryptophan synthase A, have similar leader sequences and were shown biochemically to be present in chloroplasts (11,14,21,25).…”

Section: Discussionmentioning

confidence: 99%

A Phosphoribosylanthranilate Transferase Gene Is Defective in Blue Fluorescent Arabidopsis thaliana Tryptophan Mutants

Rose

Casselman

1992

Plant Physiol.

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Section: Discussionmentioning

confidence: 99%

A Phosphoribosylanthranilate Transferase Gene Is Defective in Blue Fluorescent Arabidopsis thaliana Tryptophan Mutants

Rose

Casselman

1992

Plant Physiol.

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“…CM-2 has been proposed to be part of a complete cytosolic shikimate pathway that, in addition to supplying aromatic amino acids for protein synthesis, also provides precursors for secondary metabolism (8). This suggested that an increase in secondary metabolism might be correlated with an increase in CM-2 activity, particularly since isozymic forms of DAHP synthase demonstrated differential timing of their expression in Nicotiana silvestris suspension cultures (2,3). In these cultures, the plastid associated DAHP synthase demonstrated maximum activity during early exponential growth, whereas the cytosolic isozyme activity was greatest during late exponential growth.…”

Section: Resultsmentioning

confidence: 99%

Differential Activities of Chorismate Mutase Isozymes in Tubers and Leaves of Solanum tuberosum L.

Kuroki

Conn²

1989

Plant Physiol.

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Chromatography on DEAE cellulose equilibrated with Pipes buffer resolved three forms of chorismate mutase (CM) from tubers and leaves of Solanum tuberosum: CM-IA and CM-1B were activated by tryptophan and inhibited by phenylalanine and tyrosine; CM-2 was unaffected by these aromatic amino acids. When compared to freshly excised discs, 3 day old tuber discs demonstrated a 4.5-fold increase in CM-1 activity following wounding. By contrast, CM-2 activity levels were not affected by this treatment. In aged tuber discs the CM-1:CM-2 activity ratio was 9:1. However, in green leaves the CM-1:CM-2 activity ratio was 1:4 suggesting organ specific regulation for the expression of these isozymes. The CM-I isozymes isolated from both tubers and leaves shared similar native molecular weight values of 55,000, Km values of 40 to 56 micromolar, and inhibition by phenylalanine (110-145 micromolar concentrations required for 50% inhibition) and tyrosine (50-70 micromolar concentrations required for 50% inhibition). The resolution of CM-1 into two forms occurred only in the presence of Pipes buffer. When this buffer was replaced with Aces, Bes, imidazole or Tris, only a single peak of CM-1 activity was observed. In these buffers CM-2 eluted as a shoulder on the CM-1 peak. Analytical isoelectric focusing of the CM-1 fraction followed by assay of the gel yielded only one form of CM-1 with an isoelectric point of 5.0. Gel filtration studies with Pipes buffer yielded molecular weights of 60,000 for both CM-1A and CM-lB indicating these forms are not the result of aggregation. The two forms of CM-1 may be artifacts generated by Pipes buffer.Chorismate mutase (EC 5.4.99.5) isozymes have been well resolved by chromatography on DEAE cellulose in a number of plants (5,6,14,15). Isozyme CM2-I has been shown to be activated by tryptophan and inhibited by phenylalanine and tyrosine, whereas CM-2 is not regulated by these aromatic amino acids. However, in other studies, only CM-1 activity could be detected following anion exchange chromatography (9, 15). In a previous investigation we detected only CM-1 activity in tubers of Solanum tuberosum following DEAE cellulose chromatography in citrate-phosphate buffer (9). Recent studies with parsley cell cultures (KF McCue, EE Conn, unpublished data) indicated that CM-1 and CM-2 may coelute on DEAE cellulose. This suggested that a similar phenom- enon might be occurring in the potato system. Utilizing DEAE cellulose equilibrated with Pipes buffer, Morris et al. (12) have recently detected CM-2 in potato tubers. We also report the resolution of CM-1 and CM-2 isozymes from tubers and green leaves of S. tuberosum. The data presented in this study revealed that ofthe five buffers employed, complete resolution of tuber CM isozymes on DEAE cellulose occurred only with Pipes buffer.The separation of CM-I and CM-2 by chromatography on DEAE cellulose allowed us to observe the effects of wounding and organogenesis on the expression of these shikimate pathway enzymes. Similar studies have been reported f...

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“…The hysteric nate 7-phosphate (DAHP) synthase (EC 4.1.2.15) modulation of DS-Mn in the presence of dithio-(DS) which difTered dramatically in physical, cata-threitol was interpreted by Ganson et al (1986) to lytic and regulatory properties were first described in imply its redox regulation by thioredoxin. higher plants by Rubin & Jensen (1985), using Vigna…”

Section: Introduction ^ Similar Subcellular Compartmentation Have Beenmentioning

confidence: 99%

“…A survey of crude extracts from a variety of plant sources indicated that the DS-Co/DS-Mn isoenzyme pair may be universally present in higher plants (Ganson et al, 1986).…”

Section: Introduction ^ Similar Subcellular Compartmentation Have Beenmentioning

confidence: 99%

Synonymy of the three apparent isoenzymes of 3‐deoxy‐D‐arabino‐heptulosonate 7‐phosphate synthase in Pisum sativum L. with 3‐deoxy‐d‐manno‐octulosonate 8‐phosphate synthase and the DS‐Co/DS‐Mn isoenzyme pair

Doong

Jensen

1992

New Phytologist

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summary Three enzymes, capable of condensing phosphoenolpyruvate with erythrose 4‐phosphate, were separated by DEAE‐cellulose column chromatography of extracts from young leaves of Pisum sativum. One enzyme was identified as 3‐deoxy‐d‐manno‐octulosonate 8‐phosphate (KDOP) synthase (EC 4.1 .2.16). This novel plant enzyme mimicks 3‐deoxy‐D‐arabino‐heptulosonate 7‐phosphate synthase (EC 4.1 .2.15) in vitro by virtue of its substrate ambiguity. KDOP synthase used erythrose 4‐phosphate 28% as well as arabinose 5‐phosphate at high substrate concentrations. The pH optimum was 6.5 and divalent cations were neither required nor stimulatory. The remaining two enzymes possessed the distinctive properties of the DAHP synthase (DS) isoenzymes, DS‐Mn and DS‐Co, previously established in tobacco and spinach to be chloroplast‐ and cytosol‐localized isoenzymes, respectively. DS‐Mn was highly specific for its substrates, required dithiothreitol (a hysteretic activator) for activity, was stimulated 3.6‐fold by 0.5 mM Mn2+, and exhibited a pH optimum of 7.5. DS‐Co, by contrast, showed an extreme degree of substrate ambiguity (giving greater rates with glycolaldehyde and glyceraldehyde 3‐phosphate than with erythrose 4‐phosphate at saturating substrate concentrations), had an absolute requirement for a divalent metal, and exhibited a high pH optimum of 9.0 for catalysis.

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The Two-Isozyme System of 3-Deoxy-d-arabino-Heptulosonate 7-Phosphate Synthase in Nicotiana silvestris and Other Higher Plants

Cited by 79 publications

References 21 publications

A Phosphoribosylanthranilate Transferase Gene Is Defective in Blue Fluorescent Arabidopsis thaliana Tryptophan Mutants

A Phosphoribosylanthranilate Transferase Gene Is Defective in Blue Fluorescent Arabidopsis thaliana Tryptophan Mutants

Differential Activities of Chorismate Mutase Isozymes in Tubers and Leaves of Solanum tuberosum L.

Synonymy of the three apparent isoenzymes of 3‐deoxy‐D‐arabino‐heptulosonate 7‐phosphate synthase in Pisum sativum L. with 3‐deoxy‐d‐manno‐octulosonate 8‐phosphate synthase and the DS‐Co/DS‐Mn isoenzyme pair

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