title: Characterization of a high-affinity membrane-associated ornithine decarboxylase from the free-living nematode Caenorhabditis elegans.
abstract: Ornithine decarboxylase has been identified and characterized in the free-living nematode Caenorhabditis elegans. Unlike previously described ornithine decarboxylases, the enzyme activity is membrane-associated and remains in the membrane fraction after treatment with high salt, detergents or phosphatidylinositol-specific phospholipase C. Ornithine has an apparent Km value of 2.7 microM for ornithine decarboxylase. The enzyme is competitively inhibited by arginine and lysine with Ki values of 4.0 and 24.4 microM respectively. None of the other naturally occurring amino acids inhibited more than 10% of the enzyme activity at concentrations up to 1 mM. Agmatine, putrescine, spermidine and spermine inhibit ornithine decarboxylase in a non-competitive manner with Ki values of 10, 53.5, 59 and 855 microM respectively. A similar ornithine decarboxylase activity was also identified in membrane preparations from the parasitic nematode Haemonchus contortus.
authors.affiliation: Merck Sharp & Dohme Research Laboratories, Department of Biochemical and Molecular Parasitology, Rahway, NJ 07065.
authors.forename: J M
authors.initials: JM
authors.lastname: Schaeffer
authors.forename: M R
authors.initials: MR
authors.lastname: Donatelli
mesh_terms: D000596:Amino Acids / Q000494:pharmacology; D000818:Animals; D001120:Arginine / Q000494:pharmacology; D002107:Caenorhabditis / Q000201:enzymology*; D002451:Cell Compartmentation; D002462:Cell Membrane / Q000201:enzymology; D007700:Kinetics; D009348:Nematoda / Q000201:enzymology; D009711:Nucleotides / Q000494:pharmacology; D009952:Ornithine / Q000378:metabolism; D009955:Ornithine Decarboxylase / Q000378:metabolism*; D065108:Ornithine Decarboxylase Inhibitors; D011073:Polyamines / Q000494:pharmacology; D011700:Putrescine / Q000494:pharmacology; D012995:Solubility; D013045:Species Specificity; D013347:Subcellular Fractions / Q000201:enzymology
chemical_list: D000596:Amino Acids; D009711:Nucleotides; D065108:Ornithine Decarboxylase Inhibitors; D011073:Polyamines; D001120:Arginine; D009952:Ornithine; D009955:Ornithine Decarboxylase; D011700:Putrescine