Dolichol phosphorylation occurs via a CTP-dependent reaction in Artemia larvae

The phosphorylation of dolichol in larval stages of the brine shrimp, Artemia salina, has been investigated. The dolichol kinase has been assayed in crude microsomes; the enzyme requires CTP as phosphoryl donor and calcium as divalent cation. Activity increases with both incubation time and added microsomal protein. The product of the reaction has been characterized by chromatographic and enzymatic procedures. With gamma-32P CTP as substrate, the apparent Km for CTP is 24 microM. Enzymatic activity is stimulated fivefold by exogenous dolichol. The specific activity of the enzyme increases with the frequency of molting. Dolichol kinase activity was detectable in membranes prepared from dormant Artemia cysts. The low level in dormancy may anticipate the critical role of the enzyme during hatching.