title: A deficiency of citrate synthase results in constitutive expression of the glyoxylate pathway in Arthrobacter pyridinolis.
abstract: Previous studies of Arthrobacter pyridinolis indicated that during the first half of the growth cycle on D-fructose, the organism utilizes a respiration-coupled transport system and exhibits glyoxylate pathway activity; during the second half of the growth cycle, a phosphoenolypyruvate:D-fructose phosphotransferase system is used for transport and no glyoxylate pathway activity is found [Pelliccione et al. (1979) Eur. J. Biochem. 95, 69--75]. A citrate-synthase-deficient mutant had the following properties: (a) high constitutive levels of glyoxylate pathway enzymes on various substrates, while such levels were only found in the wild type when it was grown on acetate; (b) acetyl-CoA levels much higher than in the wild type grown on several different substrates, whereas other metabolite levels were similar in the two strains; and (c) under conditions for induction of the phosphotransferase system, the wild type exhibited at least twice as much phosphotransferase activity as the mutant strain. A mutant lacking acetyl-CoA synthetase exhibited no induction of the glyoxylate pathway in the presence of acetate, although acetate uptake was normal. The results indicate a role for acetyl-CoA as inducer of the glyoxylate pathway. They further suggest a possible role, perhaps indirect, in repression of the phosphotransferase system.
mesh_terms: D000105:Acetyl Coenzyme A / Q000378:metabolism; D001173:Arthrobacter / Q000201:enzymology* / Q000235:genetics; D002950:Citrate (si)-Synthase / Q000172:deficiency* / Q000378:metabolism; D005632:Fructose / Q000378:metabolism; D006038:Glyoxylates / Q000378:metabolism*; D007652:Oxo-Acid-Lyases / Q000172:deficiency*; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000378:metabolism
chemical_list: D006038:Glyoxylates; D005632:Fructose; D000105:Acetyl Coenzyme A; D002950:Citrate (si)-Synthase; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; D007652:Oxo-Acid-Lyases