Enzymatische Glucosylierung von pflanzlichen Sterinen

Abstract

A particulate enzyme preparation from dark grown mung bean shoots incorporates the glucosyl unit from UDP- (14C) -glucose into lipophilic products. These were identified by thin layer chromatography as a mixture of β-sitosterylglucoside and stigmasteryl-glucoside (80%) as well as the acylated forms of these substances (20%). The reaction is almost linear with time up to 10 minutes, optimal at pH values between 6.3 and 6.6 and does not require divalent cations. The acceptor sterols were shown to be present in the particulate preparation; exogenous sterols do not seem to act as acceptors. The same particulate enzyme preparation can also synthesize cellulose from UDPG 15 and lipid intermediates for its biosynthesis have been predicted 20. It appeared possible, therefore, that the sterylglucosides act as such intermediates. This, however, does not seem to be the case, since dilution of the UDP- (14C) -Glucose with unlabelled UDPG as well as its hydrolysis with phosphodiesterase within the course of an experiment demonstrates that the glucosyl units of the sterylglucosides show no turnover.