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Physical-chemical characterization and stability study of α-trypsin at pH 3.0 by differential scanning calorimetry

2007; Elsevier BV; Volume: 42; Issue: 3 Linguagem: Inglês

10.1016/j.ijbiomac.2007.12.002

1879-0003

Alexandre Martins Costa Santos, Marcos Aurélio de Santana, Felipe Tadeu Fiorini Gomide, Alexandre A. Cerqueira Miranda, José Salvador Rodrigues de Oliveira, Fabrício de Almeida Souza Vilas-Boas, André Belico de Vasconcelos, Marcelo P. Bemquerer, Marcelo M. Santoro,

thermodynamics and calorimetric analyses

alpha-Trypsin is a serine-protease with a polypeptide chain of 223 amino acid residues and six disulfide bridges. It is a globular protein with predominance of antiparallel ss-sheet secondary structure and it has two domains with similar structures. In the present work, a stability study of alpha-trypsin in the acid pH range was performed and some physical-chemical denaturation parameters were measured by using differential scanning calorimetry (DSC). The alpha-trypsin has a shelf-life (t(95%)) of about 10 months at pH 3.0 and 4 degrees C and its hydrolysis into the psi-trypsin isoform is negligible during 6 months. The observed ratio DeltaH(cal)/DeltaH(vH) is close to unity, which suggests the occurrence of a two-state transition. At pH 3.0, alpha-trypsin unfolded with T(m) = 325.9 K and DeltaH = 99.10 kcal mol(-1), and the change in heat capacity between the native and unfolded forms of the protein was estimated to be 1.96+/-0.18 kcal mol(-1)K(-1). The stability of alpha-trypsin calculated at 298 K was DeltaG(U)=6.10 kcal mol(-1) at pH 3.0. These values are in the range expected for a small globular protein. These results show that the thermodynamic parameters of unfolding of beta-trypsin do not change substantially after its conversion to alpha-trypsin.