Enzymatic acylation of steryl glycoside

Abstract

Summary A soluble protein fraction obtained from leaves of Vicia faba catalyzes the acylation of steryl glycoside to acyl steryl glycoside by acyl groups originating from galactolipids. Using semisynthetic alactolipids it was shown that both acyl groups from C-1 and C-2 of mono- and digalactosyl diglyceride are transferred to steryl glycoside. The same protein fraction was also active in the formation of acyl galactosyl diglyceride. Using the same semisynthetic galactolipids as above it was demonstrated by mass spectrometry that during formation of acyl galactosyl diglyceride the acyl groups from the donor molecules are transferred exclusively to the galactose moiety of the accepting monogalactosyl diglyceride, its diglyceride portion remaining unaltered. After working out an assay based on the transfer of tritiated oleoyl groups from digalactosyl diglyceride to steryl glycoside it was shown that most of the soluble activity in leaf homogenates was not localized in chloroplasts.