Are charged lipid-linked intermediates involved in the biosynthesis of β-glucans?

Abstract

Synthesis from UDP-[14C]glucose of charged lipid-linked glucosyl compounds by pea membranes was short-lived and of very limited magnitude compared with the synthesis of 1,4- and 1,3-linked β-glucans. Chromatographic and chemical behaviour of lipid-linked monophosphoryl glucose (Lip-P-glc), the only charged lipid formed at initial stages (30 s), was similar to that of authentic dolichol monophosphoryl glucose (Dol-P-glc). Lip-P-glc exhibited no turnover during pulse-chase experiments. Lipid-linked pyrophosphoryl glucose or pyrophosphoryl oligosaccharides were not detected. Coumarin (10 mM) caused a severe inhibition of the synthesis of sodium dodecyl sulfate soluble products and alkali-soluble and alkali-insoluble glucans, without affecting the rate of synthesis of Lip-P-glc. Transfer of the label from endogenous Lip-P-[14C]glc or from authentic Dol-P-[3H]glc into nonlipid products was minimal. It is concluded that the lipid-linked phosphoryl saccharide formed from UDP-glucose is not an obligate intermediate in the formation of β-glucans in pea membrane preparations.