ACETYL-COENZYME A - DIGITOXIN 15'-0-ACETYLTRANSFERASE FROM DIGITALIS PLANTS AND SUSPENSION-CULTURES

The enzymatic acetylation of cardenolides was investigated. Suspension cultures of Digitalis grandiflora converted digitoxin to acetylated c ardenolides such as alpha-acetyldigitoxin and lanatoside A. Protein pr eparations from the same source catalysed the transfer of an acetyl gr oup from acetyl coenzyme A to the 15'-O-position of digitoxin or digox in. The enzyme involved, acetyl coenzyme A:digitoxin 15'-O-acetyltrans ferase, was characterized and detected in protein extracts from other tissues, namely the leaves of D. grandiflora, as well as the leaves, c allus and suspended cells of D. lanata. Compartmentalization studies w ith isolated protoplasts and vacuoles revealed that the digitoxin acet yltransferase is a soluble cytosolic enzyme.