Dolichyl monophosphate and its sugar derivatives in plants

Abstract

A glucose acceptor was isolated from soya [Glycine max] beans by extraction with chloroform/methanol (2:1, vol/vol), followed by DEAE-cellulose column chromatography of the extract. This acceptor could not be distinguished from liver [pig] dolichyl monophosphate by TLC. It could replace dolichyl monophosphate as a mannose acceptor with a liver enzyme, and its glucosylated derivative could replace dolichyl monophosphate glucose as a glucose donor in the same system. These results, together with those previously reported, indicate that the acceptor from soya bean is a dolichyl monophosphate. Gel filtration of its glucosylated derivative on Sephadex G-75 in the presence of sodium deoxycholate indicated that the acceptor contained 17 or 18 isoprene units. An enzyme preparation from pea [Pisum sativum] seedlings used endogenous acceptors to form lipid phosphate sugars containing mannose and N-acetylglucosamine from GDP-mannose and UDP-N-acetylglucosamine. Chromatographic and degradative techniques indicated that the compounds formed were lipid monophosphate mannose, lipid pyrophosphate N-acetylglucosamine, lipid pyrophosphate chitobiose and a series of lipid pyrophosphate oligosaccharides containing both mannose and N-acetylglucosamine. None of these compounds was degraded by catalytic hydrogenation, and so the lipid moiety in each case was probably an .alpha.-saturated polyprenol. The endogenous acceptors for mannose and N-acetylglucosamine in peas may be dolichyl monophosphate, as was found in mammalian systems.