Abstract
Quinate:NAP(P)+-oxidoreductase (QORase, EC 1.1.1.24), which catalyzes the interconversion of quinic and 3-dehydroquinic acids, was purified from the needles and developing xylem cells of Larix sibirica. The enzymes from these two tissues were partially characterized and compared. QORase from needles had optimum pH at 9.0 and apparent Km values of 1.84 mM for quinic acid and 0.19 mM for NADP+. The enzyme was activated by phosphoenolpyruvate. Gallic and protocatechuic acids were formed in a reaction mixture of purified enzyme from needles as final products of quinic acid transformation. QORase from developing xylem cells showed pH optimum at 10.0 and had apparent Km values of 0.70 mM for quinic acid and 0.05 mM for NADP+. The enzyme was not affected by PEP. The divalent cations Co2+ and Mn2+ at least doubled activity of QORase from both sources but Mg2+ affected the enzyme from needles only. The spatial organization and regulation of quinic acid metabolism in the autotrophic and heterotrophic cells of conifers and the role of QORase in this process are discussed.
Published Version
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