QUINATE-NAP(P)(-OXIDOREDUCTASE FROM LARIX SIBIRICA - PURIFICATION, CHARACTERIZATION AND FUNCTION())

Quinate:NAP(P)(+)-oxidoreductase (QORase, EC 1.1.1.24), which catalyze s the interconversion of quinic and 3-dehydroquinic acids, was purifie d from the needles and developing xylem cells of Larix sibirica. The e nzymes from these two tissues were partially characterized and compare d. QORase from needles had optimum pH at 9.0 and apparent K-m values o f 1.84 mM for quinic acid and 0.19 mM for NADP(+). The enzyme was acti vated by phosphoenolpyruvate. Gallic and protocatechuic acids were for med in a reaction mixture of purified enzyme from needles as final pro ducts of quinic acid transformation. QORase from developing xylem cell s showed pH optimum at 10.0 and had apparent K-m values of 0.70 mM for quinic acid and 0.05 mM for NADP(+). The enzyme was not affected by P EP. The divalent cations Co2+ and Mn2+ at least doubled activity of QO Rase 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 QO Rase in this process are discussed.