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Effect of Trifluoroethanol on Native and Acid-Induced States of Glucose Oxidase from Aspergillus niger

B. Ahmad1, S. K. Haq1, A. Varshney1, A. A. Moosavi-Movahedi2, and R. H. Khan1*

1Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh 202002, India; fax: 91(571)272-1776; E-mail: rizwanhkhan@hotmail.com; rizwanhkhan1@yahoo.com

2Institute of Biochemistry and Biophysics, University of Tehran, Tehran, Iran

* To whom correspondence should be addressed.

Received June 15, 2009; Revision received July 7, 2009
We have studied the effect of trifluoroethanol (TFE) on the native (pH 7.0), acid unfolded (pH 2.6), and molten globule (pH 1.4) states of glucose oxidase (GOX) by circular dichroism and fluorescence spectroscopy. In the presence of 50% TFE, at pH 7.0 and 2.6, GOX exhibited a transition from native coiled-coil and acid unfolded state to non-associating α-helical state. Interestingly, at pH 1.4, 15% TFE induced the formation of β-structured intermediate by loss of 1-anilino-8-naphthalenesulfonate binding site and almost all tertiary contacts. The β-structured intermediate converted into open helical conformation on further addition of TFE.
KEY WORDS: glucose oxidase, molten globule, coiled-coil state, acid unfolded state, trifluoroethanol

DOI: 10.1134/S0006297910040139