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

Abstract

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 (6a R, 11a R-medicarpin), possessing the same stereochemistry as medicarpin produced in vivo.