Subcellular localization and substrate specificity of dolichol kinase from rat liver

When purified subcellular fractions were prepared from rat liver and assayed for dolichol kinase activity using pig liver dolichol as a substrate, the microsomes were found to contain the highest specific activity and greater than 75% of the total actvity. With regard to substrate specificity, the microsomal enzyme showed a marked preference for saturation of the α-isoprene: dolichol-16 and -19 were 2.5-fold more active than the corresponding polyprenols. For a given class of prenol, the 16 and 19 isoprenologs exhibited similar activity, whereas the 11 isoprenolog appeared less active. The enzyme was twice as active against the naturally occurring polyprenol-16 (α-cis-isoprene) compared to synthetic α-trans-polyprenol-16. Taken together, the data indicate that the α-isoprene specificity follows the order: saturated>cis>trans. In addition, all-trans-2,3-dihydrosolanesol was not a substrate, suggesting that at least one cis isoprene residue is required.