Abstract

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 "R (h)" 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.

Links

Publisher Full Text

Authors

Rabbani G, Ahmad E, Zaidi N, Fatima S, Khan RH

Institution

Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh 202 002, India.

Source

Cell biochemistry and biophysics 62:3 2012 Apr pg 487-99

MeSH

Anilino Naphthalenesulfonates
Calorimetry, Differential Scanning
Circular Dichroism
Guanidine
Hydrogen-Ion Concentration
Kinetics
Lipase
Protein Denaturation
Protein Folding
Protein Structure, Secondary
Protein Structure, Tertiary
Rhizopus
Spectrometry, Fluorescence

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

22215307