The enzyme ribose-phosphate pyrophosphokinase or PRPP synthetase catalyzes the conversion of ribose-5-phosphate to phosphoribosyl pyrophosphate, which is a precursor for the synthesis of purine and pyrimidine nucleotides. It is an essential enzyme that is well conserved and is found in both bacterial organisms and humans. In the thesis, we carried out the chemical denaturation of urea and monitored it with CD spectroscopy. The CD spectra show characteristic of alpha-helical protein, and that at high concentration of urea most of its secondary structure is destroyed. Denaturation by urea is reversible. Denaturation curves determined by CD spectroscopy show no dependence on protein concentration. By analyzing denaturation curves, we determined the thermodynamic stability of PRPP synthetase (standard Gibbs free energy of denaturation), which amounts to 9,7 kJ/mol.
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