ENZYMATIC FORMATION OF DEHYDRODOLICHAL AND DOLICHAL, NEW PRODUCTS RELATED TO YEAST DOLICHOL BIOSYNTHESIS

Two new polyprenyl products in addition to dehydrodolichol and dolicho l were detected by two-plate silica gel thin layer chromatography of n onpolar products formed from [1-C-14]isopentenyl diphosphate and farne syl diphosphate in the reaction with a crude 1,000 x g supernatant of yeast homogenates in the presence of NADPH. The new products were indi stinguishable from authentic dehydrodolichal and dolichal. Analyses of the time-dependent and pH-dependent formation of the four products in cluding dehydrodolichal and dolichal suggested that the biosynthetic p athway from dehydrodolichol leading to dolichal is different from that to dolichol, In double-labeled experiments with a combination of [1-C -14]isopentenyl diphosphate and a [4B-H-3]NADPH-generating system, the ratio of H-3- and C-14-derived radioactivities found in dolichal was six times higher than that in dolichol, A small amount of H-3-labeled dehydrodolichol was also detected, Considering the fact that dolichol is synthesized from dehydrodolichol (Sagami, H., Kurisaki, A., and Ogu ra, K. (1993) J. Biol, Chem. 268, 10109-10113), we propose that dehydr odolichol is a common branch point intermediate in the biosynthetic pa thways leading to dolichal and dolichol and that dehydrodolichal is an intermediate in the pathway from dehydrodolichol to dolichal.