期刊
CELL BIOCHEMISTRY AND BIOPHYSICS
卷 62, 期 3, 页码 487-499出版社
HUMANA PRESS INC
DOI: 10.1007/s12013-011-9335-9
关键词
Lipase; pH denaturation; Molten globule; Rhizopus niveus lipase; Thermal stability; GuHCl denaturation
资金
- University Grants Commission (UGC) New Delhi [32-543/2006 (SR)]
- Council of Scientific and Industrial Research (CSIR), New Delhi, India
Here, we have characterized four pH-dependent states: alkaline state, B (pH 9.0), native state, N (pH 7.4), acid-induced state, A (pH 2.2) and molten globule state, MG (pH 1.8) of Rhizopus niveus lipase (RNL) by CD, tryptophanyl fluorescence, ANS binding, DLS, and enzyme activity assay. This MG state lacks catalytic activity and tertiary structure but it has native-like significant secondary structure. The Rh of all the four states of RNL obtained from DLS study suggests that the molecular compactness of the protein increases as the pH of solution decreases. Kinetic analysis of RNL shows that it has maximum catalytic efficiency at state B which is 15-fold higher than state N. The CD and tryptophanyl fluorescence studies of RNL on GuHCl and temperature-induced unfolding reveal that the MG state is more stable than the other states. The DSC endotherms of RNL obtained at pH 9.0, 7.4, and 2.2 were with two transitions, while at pH 1.8 it showed only a single transition.
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