1-O-acyl-beta-D-glucoses as fatty acid donors in transacylation reactions

Glandular trichome exudates of the wild tomato, Lycopersicon pennellii Corr. (D'Arcy), are composed of 2,3,4-tri-O-acylglucoses possessing short to medium chain length (C4-C12) straight- and branched-chain fatty acids. These fatty acids are activated via a UDP-glucose-dependent reaction to form their respective high-energy 1-O-acyl-beta-D-glucopyranose derivatives. The activated 1-O-acyl moieties are then transacylated to other glucose and/or partially acylated glucose derivatives. Here we demonstrate that 1-O-acyl-beta-D-glucopyranoses participate in two types of glucose transacylation reactions. The first is anomeric exchange of the acyl moiety from 1-O-acyl-beta-D-glucopyranose to beta-glucose. The second is disproportionation between two molecules of 1-O-acyl-beta-D-glucopyranose resulting in formation of diacylglucose and glucose. Leaf extracts from cultivated tomato (Lycopersicon esculentum), which does not accumulate epicuticular acylglucoses, possess low levels of both the acyl exchange and disproportionation activities.