Enhanced chick oviduct dolichol kinase activity during estrogen-induced differentiation

Crude microsomal preparations from hen oviduct catalyze the transfer of [32P]phosphate from [gamma-32P]CTP or [gamma-32P]dCTP to endogenous dolichol, forming dolichyl [32P]monophosphate. The oviduct kinase activity assayed with [gamma-32P]CTP is stimulated by divalent cations and exogenous dolichol. The enzymatic formation of dolichyl [32P]monophosphate is inhibited by dCDP and CDP, but not CMP, ADP, GDP, or UDP. The hen oviduct kinase is inhibited 50% by the addition of 38 microM CDP, but 101 microM dCDP is required for 50% inhibition. The amount of dolichol kinase activity in chick oviduct microsomes increases 3.7-fold within 10 days of estrogen administration. The hormone-induced increase in kinase activity is also observed when membranes from untreated and estrogen-treated chicks are assayed in the presence of saturating levels of exogenous dolichol. The microsomal preparations from oviducts of untreated chicks and fully induced birds both exhibit an apparent Km value of 7.1 microM for CTP. An apparent Km of 14 microM has been determined for dCTP. Thus, the developmental change in dolichol kinase activity does not appear to be the result of a difference in the amount of available endogenous dolichol or an alteration in the reactive site for the nucleoside triphosphate substrate, but is probably due to an increased level of the enzyme.