• Interaction of rose bengal with mung bean aspartate transcarbamylase

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    • Keywords

       

      Mung bean; aspartate transcarbamylase; interactions; active site; rose bengal; allosteric

    • Abstract

       

      The fluorescein dye, rose bengal in the dark: (i) inhibited the activity of mung bean aspartate transcarbamylase (EC 2.1.3.2) in a non-competitive manner, when aspartate was the varied substrate; (ii) induced a lag in the time course of reaction and this hysteresis was abolished upon preincubation with carbamyl phosphate; and (iii) converted the multiple bands observed on polyacrylamide gel electrophoresis of enzyme into a single band. The binding of the dye to the enzyme induced a red shift in the visible spectrum of dye suggesting that it was probably interacting at a hydrophobic region in the enzyme. The dye, in the presence of light, inactivated the enzyme and the inactivation was not dependent on pH. All the effects of the dye could be reversed by UMP, an allosteric inhibitor of the enzyme. The loss of enzyme activity on photoinactivation and the partial protection afforded by N-phosphonoacetyl-L-aspartate, a transition state analog and carbamyl phosphate plus succinate, a competitive inhibitor for aspartate, as well as the reversal of the dye difference spectrum by N-phosphonoacetyl-L-aspartate suggested that in the mung bean aspartate transcarbamylase, unlike in the case ofEscherichia coli enzyme, the active and allosteric sites may be located close to each other.

    • Author Affiliations

       

      P V Prasad1 2 N Appaji Rao1

      1. Department of Biochemistry, Indian Institute of Science, Bangalore - 560 012, India
      2. Department of Biochemistry, Scripps Clinic and Research Foundation, LaJolla, California - 92037, USA
    • Dates

       
  • Journal of Biosciences | News

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