title: Repression-dependent alteration of an arginine enzyme in Escherichia coli.
abstract: Treatment of susceptible Escherichia coli K12 derivatives with 0.4 M Mg(++) at 37 degrees , potentiated by L-arginine or L-canavanine, leads to alteration of acetylornithine delta-transaminase. The alteration, obtained in the absence of protein synthesis and reversible at 0 or 37 degrees , is manifested in extracts by lowered activity and modified substrate affinity behavior of the enzyme without gross changes in sedimentation properties. Cells grown under arginine repression are susceptible to the treatment; cells grown under genetic or steady-state physiological derepression are not. Transaminase synthesized during early derepression can be altered, although to progressively diminishing extents. Enzyme formed under steady-state derepression becomes alterable following transition to repression. The Mg(++) -dependent alteration can be thought to arise while the enzyme, arginine (or canavanine), and aporepressor are in contact, and to reflect a physiological process such as the participation of the enzyme in the repressive complex.
mesh_terms: D001120:Arginine / Q000494:pharmacology*; D004794:Enzyme Repression / Q000187:drug effects*; D004926:Escherichia coli / Q000201:enzymology*; D008274:Magnesium / Q000494:pharmacology; D013995:Time; D000637:Transaminases / Q000378:metabolism
chemical_list: D001120:Arginine; D000637:Transaminases; D008274:Magnesium