Cardiac glycoside interconversions at the subcellular level in Convallaria majailis

Further evidence for the biosynthetic sequence periplorhamnoside → convallatoxol → convallatoxin, proposed after experiments in vivo, was obtained with subcellular fractions of Convallaria majalis leaves. A NADPH-dependent monooxygenase tentatively localized on mitochondrial membranes converted periplorhamnoside into convallatoxol. In contrast the enzyme transforming convallatoxol into convallatoxin could be detected only in the soluble fraction. The conversion required NAD as a cofactor, thus the specifity observed is that of an alcohol dehydrogenase.