title: Participation of branched-chain amino acid analogues in multivalent repression.
abstract: Two isoleucine analogues and two leucine analogues were examined for their ability to replace the natural amino acid preventing the accumulation of threonine deaminase-forming potential. The procedure used to study repression by the analogues distinguishes between true repression and the formation of inactive enzyme by the analogue in question. The leucine analogue 4-azaleucine was found to replace leucine in multivalent repression of threonine deaminase-forming potential in Escherichia coli but not in Salmonella typhimurium. Another leucine analogue, trifluoroleucine, was only partially effective in causing repression in either organism. The isoleucine analogue 4-azaisoleucine was ineffective in replacing isoleucine in repression. In contrast, 4-thiaisoleucine effectively replaced isoleucine in the repression of threonine deaminase-forming potential in S. typhimurium and E. coli.
mesh_terms: D000603:Amino Acids, Sulfur / Q000494:pharmacology; D001372:Aza Compounds / Q000494:pharmacology; D001426:Bacterial Proteins / Q000096:biosynthesis; D002250:Carbon Radioisotopes; D004794:Enzyme Repression / Q000187:drug effects; D004926:Escherichia coli / Q000201:enzymology; D006836:Hydro-Lyases / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D007532:Isoleucine / Q000494:pharmacology*; D007930:Leucine / Q000494:pharmacology*; D009876:Operon / Q000187:drug effects; D012486:Salmonella typhimurium / Q000201:enzymology; D013912:Threonine; D013997:Time Factors
chemical_list: D000603:Amino Acids, Sulfur; D001372:Aza Compounds; D001426:Bacterial Proteins; D002250:Carbon Radioisotopes; D007532:Isoleucine; D013912:Threonine; D006836:Hydro-Lyases; D007930:Leucine