title: Ornithine decarboxylase encoded by chlorella virus PBCV-1.
abstract: Sequence analysis of the 330-kb genome of chlorella virus PBCV-1 revealed an open reading frame, A207R, which encodes a protein with 37-41% amino acid identity to ornithine decarboxylase (ODC) from many eukaryotic organisms. The a207r gene was cloned and the protein was expressed as a His-A207R fusion protein in Escherichia coli. The recombinant protein catalyzes pyridoxal 5'-phosphate-dependent decarboxylation of ornithine to putrescine, the first step in the polyamine biosynthetic pathway. The enzyme has a pH optimum of 9.0 and a temperature optimum of 42 degrees C, and it requires dithiothreitol for maximal activity. The enzyme has a K(m) for ornithine of 0.78 mM and a specific activity of 100 micromol/min/mg protein. PBCV-1 ODC is quite sensitive to the competitive inhibitor L-arginine and the irreversible inhibitor difluoromethylarginine but it is less sensitive to the irreversible inhibitor difluoromethylornithine. The a207r gene is expressed both early and late in PBCV-1 infection and is highly conserved among the chlorella viruses. The 42-kDa PBCV-1 ODC (372 amino acids) is the smallest ODC in the databases and, to our knowledge, is the first virus-encoded ODC.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002708:Chlorella / Q000821:virology*; D006801:Humans; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D009955:Ornithine Decarboxylase / Q000737:chemistry / Q000235:genetics*; D065108:Ornithine Decarboxylase Inhibitors; D017862:Phycodnaviridae / Q000145:classification / Q000201:enzymology*; D010802:Phylogeny; D011994:Recombinant Proteins / Q000096:biosynthesis
chemical_list: D065108:Ornithine Decarboxylase Inhibitors; D011994:Recombinant Proteins; D009955:Ornithine Decarboxylase