Characterization of acid-induced unfolding intermediates of glucose/xylose isomerase.

摘要: Acid-induced unfolding of the tetrameric glucose/xylose isomerase (GXI) from Streptomyces sp. NCIM 2730 has been investigated using intrinsic fluorescence, fluorescence quenching, second derivative spectroscopy, hydrophobic dye (1-anilino-8-naphthalene-sulfonate) binding and CD techniques. The pH dependence tryptophanyl GXI at different temperatures indicated presence two stable intermediates 5.0 3.0. 3.2 intermediate was a dimer exhibited molten globule-like characteristics, such as native-like secondary structure, loss tertiary increased exposure pockets, altered microenvironment tyrosine residues accessibility to quenching by acrylamide. Fluorescence studies on suggested involvement partially folded state in native globule transition. retained considerable structure compared state. This characterized its capacity, which is smaller than state, but greater that shared dimeric status prone aggregate formation evident Rayleigh light scattering studies. Based these results, pathway can be illustrated as: N-->PFI-->MG-->U; where N 7.5; PFI 5.0; MG U monomeric unfolded obtained 6 M GdnHCl. Our results demonstrate existence multimeric alpha/beta barrel protein.