Investigation the structure and stability of Carboxypeptidase A on presence of Putrescine

Polyamines such as putrescine can have interaction with proteins. The aim of the present study was to investigate how putrescine could influence the structure and thermal stability of carboxypeptidase A (CPA). CPA (EC 3.4.17.1) is a zinc-containing proteolytic enzyme that was isolated in the pure crystalline form in 1937 and was the first metalloprotease and second zinc enzyme to be identified. The UV-spectroscopy, thermal denaturation and thermodynamics studies were conducted to investigate the effect of putrescine on the structure and thermal stability of CPA, in 25 mM Tris-HCl buffer, with the pH 7.5. The UV-spectroscopy results show that the stability (Tm) of CPA was increased in the presence of putrescine in the range 303-353 K in the tris-HCl buffer and pH 7.5. The analysis of UV-Vis indicates that by increasing concentration of putrescine, absorption was decreased. Thermodynamic parameters showed static quenching during putrescine binding. The thermodynamic parameters changes, including Gibbs free-energy (ΔG°), entropy (ΔS°) and enthalpy (ΔH°), showed that the binding of putrescine to CPA was spontaneous and the hydrogen bonding and van der Waals interactions played a major role in stabilizing the CPA-putrescine complex. The value of n was approximately equal to 1, indicating that there was one single binding site in CPA for putrescine during their interaction. As a result, putrescine could be considered as an a stabilizer for CPA.

کلیدواژه ها:

Carboxypeptidase A ، Putrescine ، Spectroscopic techniques ، Thermodynamics