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Some regulatory properties of pea leaf carbamoyl phosphate synthetase

Thomas Denny O'Neal ; Naylor, Aubrey W.

Plant physiology (Bethesda), 1976, Vol.57 (1), p.23-28 [Periódico revisado por pares]

United States: American Society of Plant Physiologists

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  • Título:
    Some regulatory properties of pea leaf carbamoyl phosphate synthetase
  • Autor: Thomas Denny O'Neal ; Naylor, Aubrey W.
  • Assuntos: Enzyme stability ; Enzymes ; Escherichia coli ; Nucleotides ; Peas ; Phosphates ; Pyrimidine nucleotides ; Quaternary ammonium compounds ; Seedlings ; Sulfates
  • É parte de: Plant physiology (Bethesda), 1976, Vol.57 (1), p.23-28
  • Notas: F60
    F
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  • Descrição: Carbamoyl phosphate synthetase of pea shoots (Pisum sativum L.) was purified 101-fold. Its stability was greatly increased by the addition of substrates and activators. The enzyme was strongly inhibited by micromolar amounts of UMP (Ki less than 2 μM). UDP, UTP, TMP, and ADP were also inhibitory. AMP caused either slight activation (under certain conditions) or was inhibitory. Uridine nucleotides were competitive inhibitors, as was AMP, while ADP was a noncompetitive inhibitor. Enzyme activity was increased manyfold by the activator ornithine. Ornithine acted by increasing the affinity for Mg·ATP by a factor of 8 or more. Other activators were IMP, GMP, ITP, and GTP. IMP, like ornithine, increased the Michaelis constant for Mg·ATP. The activators ornithine, GMP, and IMP (but not GTP and ITP) completely reversed inhibition caused by pyrimidine nucleotides while increasing the inhibition caused by ADP and AMP.
  • Editor: United States: American Society of Plant Physiologists
  • Idioma: Inglês

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