pH-Dependent urea-induced unfolding of stem bromelain: unusual stability against urea at neutral pH.
Equilibrium unfolding of stem bromelain (SB) with urea as a denaturant has been monitored as a function of pH using circular dichroism and fluorescence emission spectroscopy. Urea-induced denaturation studies at pH 4.5 showed that SB unfolds through a two-state mechanism and yields DeltaG (free energy difference between the fully folded and unfolded forms) of approximately 5.0 kcal/mol and C(m) (midpoint of the unfolding transition) of approximately 6.5 M at 25 degrees C. Very high concentration of urea (9.5 M) provides unusual stability to the protein with no more structural loss and transition to a completely unfolded state.
Ahmad
B
B
Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh, 202002, India.
Rathar
G M
GM
Varshney
A
A
Khan
R H
RH
D001963:Bromelains / Q000737:chemistry*; D002942:Circular Dichroism; D006863:Hydrogen-Ion Concentration; D011489:Protein Denaturation; D055550:Protein Stability; D013050:Spectrometry, Fluorescence; D013816:Thermodynamics; D014508:Urea / Q000737:chemistry*
D014508:Urea; D001963:Bromelains; C091760:stem bromelain