Reaction of optically active S- and R-forms of dolichyl phosphates with activated sugars

Chemical synthesis was used to produce optically active isomers of dolichol (S- and R-forms) with 18 and 19 isoprene residues. The phosphorylated polyprene was studied in rat liver microsomal GDP-mannosyl and UDP-N-acetylglucosaminyl transferase systems. The two dolichol-P forms in both transferase systems gave Vmax values which for the S-form exceeded 4-6 times what was obtained with the R-form. The Km values were also higher for the S-form. The hepatocyte appears to contain a large excess of dolichyl-P, by 100 times exceeding that of the Km values. For this reason the S-form of dolichyl-P seems to be one of the requirements for the normal establishment of the N-glycosidically linked oligosaccharide chain.