Regulation of Purine Ribonucleotide Synthesis by End Product Inhibition:III. Effect of Purine Nucleotides on Succino-AMP Synthetase of <i>Bacillus subtilis</i>

J-STAGE
  • ISHII Kenji
    The Central Research Laboratories of Ajinomoto Co., Inc.
  • SHIIO Isamu
    The Central Research Laboratories of Ajinomoto Co., Inc.

抄録

1. Succino-AMP synthetase [EC 6. 3. 4. 4] was partially purified from the adenine starved cells of a Bacillits subtilis mutant which was derived from K strain and lacking succino-AINIP lyase [EC 4. 3. 2. 2]. The enzyme was stabilized by the presence of 1 myr dithiothreitol. Optimum pH for activity was about 7.5. Apparent Michaelis constants for IMP, GTP and L-aspartic acid were 34μM, 73μM and 680μM, respectively.<br> 2. The enzyme was inhibited strongly by the end products, AMP and ADP. Complete inhibition was obtained by 0.3 mM AMP. The inhibition by AMP was competitive to GTP, noncompetitive to L-aspartic acid and of a miffed type to IMP. Both the Lineweaver-Burk plots in the presence of AMP and rate-AMP concentration curve were normal. Succino-AMP, GDP and inorganic orthophosphate, which are the direct product of the reaction, were also inhibitory at higher concentrations.

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