The 'pterocarpan synthase' of alfalfa: association and co-induction of vestitone reductase and 7,2'-dihydroxy-4'-methoxy-isoflavanol (DMI) dehydratase, the two final enzymes in medicarpin biosynthesis.

Vestitone reductase and 7,2'-dihydroxy-4'-methoxy-isoflavanol (DMI) dehydratase are the two final enzymes in medicarpin biosynthesis in alfalfa (Medicago sativa). Although two independent enzymes, vestitone reductase and DMI dehydratase can be loosely associated in low ionic strength buffers, presumably by a weak protein-protein interaction. The activities of vestitone reductase and DMI dehydratase increased approximately 3-fold 6 hours after elicitor treatment in alfalfa suspension cell culture. The activities remained at maximal levels for 40 hours, correlating with a steady increase in the medicarpin content of the cells. Medicarpin produced in vitro from vestitone by the action of vestitone reductase and DMI dehydratase was found to be (-)-medicarpin (6aR,11aR-medicarpin), possessing the same stereochemistry as medicarpin produced in vivo.