Trifluoroethanol increases the stability of Delta(5)-3-ketosteroid isomerase. 15N NMR relaxation studies.
In the equilibrium unfolding process of Delta(5)-3-ketosteroid isomerase from Pseudomonas testosteroni by urea, it was observed that the enzyme stability increases by 2.5 kcal/mol in the presence of 5% trifluoroethanol (TFE). To elucidate the increased enzyme stability by TFE, the backbone dynamics of Delta(5)-3-ketosteroid isomerase were studied in the presence and absence of 5% TFE by (15)N NMR relaxation measurements, and the motional parameters (S(2), tau(e), and R(ex)) were extracted from the relaxation data using the model-free formalism. The presence of 5% TFE causes little change or a slight increase in the order parameters (S(2)) for a number of residues, which are located mainly in the dimer interface region. However, the majority of the residues exhibit reduced order parameters in the presence of 5% TFE, indicating that high frequency (pico- to nanosecond) motions are generally enhanced by TFE. The results suggest that the entropy can be an important factor for the enzyme stability, and the increase in entropy by TFE is partially responsible for the increased stability of Delta(5)-3-ketosteroid isomerase.
Yun
Sunggoo
S
Department of Chemistry, Pohang University of Science and Technology, Pohang, 790-784, Korea.
Jang
Do Soo
DS
Choi
Gildon
G
Kim
Kwang S
KS
Choi
Kwan Yong
KY
Lee
Hee Cheon
HC
D004058:Diffusion; D004795:Enzyme Stability; D009682:Magnetic Resonance Spectroscopy; D017510:Protein Folding; D012399:Rotation; D013251:Steroid Isomerases / Q000737:chemistry*; D014270:Trifluoroethanol / Q000494:pharmacology*; D014508:Urea / Q000494:pharmacology
D014270:Trifluoroethanol; D014508:Urea; D013251:Steroid Isomerases; C022660:steroid delta-isomerase