Distribution And Metabolism Of Polyisoprenoid Alcohols In Plants

The phosphorylated derivatives of (alpha)-unsaturated polyisoprenoid alcohols (polyprenols) are obligatory intermediates in the biosynthesis of cell wall glycans in bacteria, whereas (alpha)-saturated polyisoprenoid alcohols (dolichols) are essential intermediates in the biosynthesis of asparagine-linked glycoproteins in eucaryotic organisms. Although a number of polyisoprenoid alcohols from plants have been characterized, there is much more to learn about the distribution, metabolism and function of polyisoprenoid alcohols in plants.;Polyisoprenoid alcohols were isolated from seeds of different plant species and purified by high pressure liquid chromatography. The presence of dolichols in dicotyledonous seeds, and both dolichols and polyprenols in monocotyledonous seeds was established by nuclear magnetic resonance and infrared spectral analysis. The amounts of polyisoprenoid alcohol present in various seeds ranged from 1 to 16 mg/100 g of seeds.;The formation of dolichyl pyrophosphate linked oligosaccharides and three new proteins were demonstrated in soybeans during germination. These observations support the existence of dolichol dependent glycosylation in plants.;The fate of dolichols during germination was investigated using the soybean as a model. The dolichol content of germinating soybeans gradually decreased over the first three days of germination, whereas the concentration of dolichyl phosphate rose from undetectable levels to 1.4 (mu)g/seedling. This suggests that during germination endogenous dolichol may be phosphorylated by a kinease.;Dolichol kinase and dolichyl phosphate phosphatase (Dol-P phosphatase) activities were identified in soybean microsomes and both enzymes were characterized. The activities of dolichol kinase and Dol-P phosphatase were measured throughout germination. An increase in dolichol kinase activity was observed up to three days of germination and the activity then gradually decreased. Dol-P phosphatase activity gradually increased up to day three of germination and remained at high levels.;The submicrosomal distribution of Dol-P phosphatase and dolichol kinase activities was investigated. The high activities of Dol-P phosphatase and dolichol kinase found in rough endoplasmic reticulum could provide a mechanism for regulation of Dol-P concentration by a phosphorylation and dephosphorylation mechanism. The controlled Dol-P levels in turn may regulate the biosynthesis of asparagine-linked glycoproteins during germination