title: Characterization of polyisoprenyl phosphate phosphatase activity in rat liver.
abstract: The polyisoprenyl phosphate dephosphorylating activity of rat liver has been investigated with regard to substrate specificity, subcellular distribution, and transmembrane orientation. Total liver microsomes were employed as a source of enzymatic activity against a variety of 32P-labeled substrates. Susceptibility to dephosphorylation followed the order solanesyl phosphate greater than alpha-cis-polyprenyl 19-phosphate = alpha-trans-polyprenyl 19-phosphate = dihydrosolanesyl phosphate greater than (S)-dolichyl 19-phosphate = (R)-dolichyl 19-phosphate = (R,S)-dolichyl 11-phosphate. There appeared to be no major effect of chain length from 11 to 20 isoprenes. Data obtained from inhibition studies using solanesyl [32P]phosphate as substrate were consistent with the substrate specificity studies and suggested that a single activity is responsible. With dolichyl [32P]phosphate as substrate, the phosphatase specific activity of the subcellular fractions prepared from rat liver was found to follow the sequence Golgi = smooth endoplasmic reticulum greater than plasma membrane greater than lysosomes = rough endoplasmic reticulum greater than nuclei greater than mitochondria. Transmembrane topography studies, using enzyme latency as a criterion, were consistent with an orientation of the active site facing the cytoplasm.
mesh_terms: D000818:Animals; D002451:Cell Compartmentation; D004288:Dolichol Phosphates / Q000378:metabolism; D004286:Dolichols / Q000378:metabolism; D007425:Intracellular Membranes / Q000201:enzymology / Q000648:ultrastructure; D008360:Mannosephosphates / Q000378:metabolism; D008862:Microsomes, Liver / Q000201:enzymology* / Q000648:ultrastructure; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D011106:Polyisoprenyl Phosphates / Q000378:metabolism; D051381:Rats; D013379:Substrate Specificity
chemical_list: D004288:Dolichol Phosphates; D004286:Dolichols; D008360:Mannosephosphates; D011106:Polyisoprenyl Phosphates; C048154:solanesyl phosphate; D010744:Phosphoric Monoester Hydrolases; C020088:dolichyl-phosphatase