THE PTEROCARPAN SYNTHASE OF ALFALFA - ASSOCIATION AND COINDUCTION OF VESTITONE REDUCTASE AND 7,2'-DIHYDROXY-4'-METHOXY-ISOFLAVANOL (DMI) DEHYDRATASE, THE 2 FINAL ENZYMES IN MEDICARPIN BIOSYNTHESIS

Vestitone reductase and 7,2'-dihydroxy-4'-methoxy-isoflavanol (DMI) de hydratase are the two final enzymes in medicarpin biosynthesis in alfa lfa (Medicago sativa). Although two independent enzymes, vestitone red uctase and DMI dehydratase can be loosely associated in low ionic stre ngth buffers, presumably by a weak protein-protein interaction. The ac tivities of vestitone reductase and DMI dehydratase increased approxim ately 3-fold 6 hours after elicitor treatment in alfalfa suspension ce ll culture. The activities remained at maximal levels for 40 hours, co rrelating with a steady increase in the medicarpin content of the cell s. Medicarpin produced in vitro from vestitone by the action of vestit one reductase and DMI dehydratase was found to be (-)-medicarpin (6aR, 11aR-medicarpin), possessing the same stereochemistry as medicarpin pr oduced in vivo.