Turkish Journal of Biology




Two cysteine residues were introduced to selected positions (Serine-309 and Serine-43) of the Thermoplasma acidophilum citrate synthase. Serine-309 Cysteine mutation drastically reduced the activity, as well as the thermostabiity of the enzyme. Although Serine-43 Cysteine mutation reduced the enzyme activity, it did not have any effect on the thermostability. Both wild-type and cysteine-43 mutant Thermoplasma citrate synthase enzymes were purified to homogenity using affinity chromatography on Matrex Gel Red A. The cysteine-43 mutant Thermoplasma citrate synthase was strikingy similar to the wild-type recombinant citrate synthase in its molecular size, substrate and co-factor specificities, pH profile and thermal resistance. The decrease in the specific activity of the citrate synthase as a result of this mutation was reflected by V max and E a values.


Thermostability, Thermoplasma acidophium, citrate synthase, site-specific mutagenesis.

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