title: Regulatory mutations affecting ornithine decarboxylase activity in Saccharomyces cerevisiae.
abstract: We isolated several strains of Saccharomyces cerevisiae containing mutations mapping at a single chromosomal gene (spe10); these strains are defective in the decarboxylation of L-ornithine to form putrescine and consequently do not synthesize spermidine and spermine. The growth of one of these mutants was completely eliminated in a polyamine-deficient medium; the growth rate was restored to normal if putrescine, spermidine, or spermine was added. spe10 is not linked to spe2 (adenosylmethionine decarboxylase) or spe3 (putrescine aminopropyltransferase [spermidine synthease]). spe 10 is probably a regulatory gene rather than the structural gene for ornithine decarboxylase, since we isolated two different mutations which bypassed spe10 mutants; these were spe4, an unliked recessive mutation, and spe40, a dominant mutation linked to spe10. Both spe4 and spe40 mutants exhibited a deficiency of spermidine aminopropyltransferase (spermine synthase), but not of putrescine aminopropyltransferase. This suggests that ornithine decarboxylase activity is negatively controlled by the presence of spermidine aminopropyltransferase.
mesh_terms: D002262:Carboxy-Lyases / Q000235:genetics*; D005809:Genes, Regulator; D008040:Genetic Linkage; D009154:Mutation; D009955:Ornithine Decarboxylase / Q000235:genetics* / Q000378:metabolism; D011700:Putrescine / Q000096:biosynthesis; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D013095:Spermidine / Q000494:pharmacology; D013096:Spermine / Q000494:pharmacology; D013097:Spermine Synthase / Q000378:metabolism
chemical_list: D013096:Spermine; D013097:Spermine Synthase; D002262:Carboxy-Lyases; D009955:Ornithine Decarboxylase; D013095:Spermidine; D011700:Putrescine