In silico, in vitro, and structural investigations on BAHD-enzymes from different species able to malonylate 21-hydroxypregnanes

BAHD-acyltransferases represent a large enzyme family found ubiquitously in angiosperms. They are considered substrate-promiscuous, accepting various substrates ranging from small aliphatic alcohols to complex structures such as terpenoids or flavonoids. BAHDs catalyze the formation of esters using different acyl-CoA thioesters and are thus important enzymes of specialized plant metabolism [1]. It is assumed that one step in cardenolide formation, the 21-O-malonylation of 21-hydroxypregnanes, is catalyzed by a BAHD-malonyltransferase (21MaT).