3-Deoxy-d-arabino-Heptulosonate 7-Phosphate Synthase from Potato Tuber (Solanum tuberosum L.)

Abstract

3-Deoxy-D-arabino-heptulosonate 7-phosphate synthase, the first enzyme of the shikimate pathway, was purified to electrophoretic homogeneity from tubers of Solanum tuberosum L. cv Superior. The enzyme is a dimer with a native molecular weight of 110,000. (7). This enzyme catalyzes the condensation of P-enolpyruvate and erythrose-4-P to DAHP and Pi, the first reaction in the biosynthesis of aromatic compounds (20). The enzyme has been purified to homogeneity from several prokaryotic sources (7); in Escherichia coli, this activity exclusively controls the carbon flow into the shikimate pathway (12).In higher plants, the shikimate pathway provides precursors not only for the synthesis of the aromatic amino acids, but also for a variety of secondary metabolites such as lignins, alkaloids, coumarins, flavonoids, and indole derivatives (25). DAHP synthase activity has been demonstrated in several higher plants (2, 6, 9, 13-17, 22, 23); the enzyme has been extensively purified from Brassica oleracea (9), and has recently been obtained in homogeneous form from Daucus carota (23

Redox Regulation of Arabidopsis 3-Deoxy-d-arabino-Heptulosonate 7-Phosphate Synthase

“…Plant DAHP synthase was first purified to homogeneity from carrot (Daucus carota) roots and potato (Solanum tuberosum) tubers (Suzich et al, 1985;Pinto et al, 1986). Polyclonal antibodies specific for this protein were used to obtain cDNA encoding DAHP synthase (Dyer et al, 1990).…”

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

“…Recently, Solanum tuberosum was described as an apparent exception where only one DAHP synthase was found (Pinto, Suzich & Herrmann, 1986). A later study by Morris, Doong & Jensen (1989Z)) with potato, however, showed potato tissue to possess DS-Mn and DS-Co isoenzymes that displayed the defining properties previously found in mung bean and tobacco.…”

“…Thus, it has been surprising that in several cases where only one isoenzyme was detected and purified (Huisman & Kosuge, 1974;Pinto et al, 1986), it appears that DS-Co was the species which was overlooked. Our findings of precipitation of DS-Co by protamine sulphate may explain this, since 0-2 "o protamine sulphate was used in the protocols of purification used in both the aforementioned cauliflower and potato studies.…”

Wounding Induces One of Two Isoenzymes of 3-Deoxy-d-arabino-Heptulosonate 7-Phosphate Synthase in Solanum tuberosum L.

“…Plant DAHP synthases are not inhibited by the aromatic amino acids (20,28), but two DAHP synthase isoenzymes are distinguishable through their metal requirements and their sensitivity to various metabolic intermediates in a variety ofplants (8). DAHP synthaseMn is specifically activated by Mn2' and inhibited by arogenate (8), whereas DAHP synthase-Co requires Co2+, Mg2",or another divalent cation for activity and is sensitive to dehydroxycinnamate (23).…”

“…Studies on the subcellular localization of the isoenzymes suggest that the Mn2+-activated form is plastidic and that the other form is cytosolic ( 17). DAHP synthase-Mn was purified to electrophoretic homogeneity from carrot (Daucus carota) (28) and potato (Solanum tuberosum) (20). Monospecific polyclonal antibodies against the potato enzyme (19) served to screen a Xgtl 1-derived cDNA library for a clone encoding potato DAHP synthase (7).…”