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    • Fulltext

       

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      Permanent link:
      https://www.ias.ac.in/article/fulltext/jbsc/003/02/0179-0190

    • Keywords

       

      Serine hydroxymethyltransferase; circular dichroism; thermal stability; conformational transitions

    • Abstract

       

      The homogeneous serine hydroxymethyltransferase from monkey liver was optimally activate at 60°C and the Arrhenius plot for the enzyme was nonlinear with a break at 15°C. The monkey liver enzyme showed high thermal stability of 62°C, as monitored by circular dichroism at 222 nm, absorbance at 280 nm and enzyme activity. The enzyme exhibited a sharp co-operative thermal transition in the range of 50°–70°(Tm= 65°C), as monitored by circular dichroism. L-Serine protected the enzyme against both thermal inactivation and thermal disruption of the secondary structure. The homotropic interactions of tetrahydrofolate with the enzyme was abolished at high temperatures (at 70°C, the Hill coefficient value was 1.0). A plot ofh values vs. assay temperature of tetrahydrofolate saturation experiments, showed the presence of an intermediate conformer with anh value of 1.7 in the temperature range of 45°–60°C. Inclusion of a heat denaturation step in the scheme employed for the purification of serine hydroxymethyltransferase resulted in the loss of cooperative interactions with tetrahydrofolate. The temperature effects on the serine hydroxylmethyltransferase, reported for the first time, lead to a better understanding of the heat induced alterations in conformation and activity for this oligomeric protein.

    • Author Affiliations

       

      Kashi S Ramesh1 2 V S Ananthanarayanan1 3 N Appaji Rao1

      1. Department of Biochemistry, Indian Institute of Science, Bangalore - 560 012
      2. Hematology Research Laboratory, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA
      3. Department of Biochemistry, Memorial University of Newfoundland, St. John’s, Newfoundland - A1B 3X9, Canada

    • Dates

       
      Published
      June 1981
      Manuscript received
      11 February 1981

  • Journal of Biosciences | News

      Forthcoming Special issue.


    • To trigger further research on plant mitochondria, the Journal of Biosciences is bringing out a special issue titled "Plant Mitochondria: Properties and Interactions with Other Organelles".


      Plant mitochondria are quite distinct and have unique features, such as a cyanide-insensitive alternate pathway. They also interact with chloroplasts to optimize photosynthetic carbon assimilation.


      Submissions are welcome until 30 July 2023. The contributions can be original articles, short communications, reviews, or mini-reviews on any topic related to plant mitochondria.


      Authors can submit their articles online at https://www.editorialmanager.com/jbsc/default2.aspx

      Posted on April 12, 2023
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      Posted on July 25, 2019

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