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Formation of molten globule-like state during acid denaturation of Aspergillus niger glucoamylase

Paper ID Volume ID Publish Year Pages File Format Full-Text
34571 45034 2012 10 PDF Available
Title
Formation of molten globule-like state during acid denaturation of Aspergillus niger glucoamylase
Abstract

Acid denaturation of Aspergillus niger glucoamylase was studied using different conformational probes. Both far-UV CD spectral signal (MRE222 nm) and tryptophan fluorescence remained unchanged in the pH range, 7.0–3.0 but decreased significantly below pH 3.0, whereas ANS fluorescence showed a marked increase below pH 1.5. Maximal changes in MRE222 nm and ANS fluorescence were noticed at pH 1.0. Acid-denatured state of glucoamylase at pH 1.0 retained a significant amount of secondary structure as reflected from far-UV CD spectra but showed a deformed tertiary structure with significant exposure of nonpolar groups as well as tryptophan residues as revealed by increased ANS fluorescence, decreased tryptophan fluorescence and three-dimensional fluorescence spectral signals and increase in Ksv value in acrylamide quenching experiments. Acid-denatured state showed no significant variation in the CD spectral signal throughout the temperature range, 0–100 °C. However, a late cooperative transition was observed upon GdnHCl treatment, compared to the native enzyme. All these results suggested that the acid-denatured state of glucoamylase at pH 1.0 represented the molten globule-like state.

► First report on the complete acid denaturation of Aspergillus niger glucoamylase. ► Characterization of molten globule state of the enzyme at pH 1.0 for the first time. ► Use of far-UV and near UV CD spectra, ANS fluorescence and intrinsic fluorescence. ► Thermal denaturation, acrylamide quenching and 3-D fluorescence studies.

Keywords
ANS, 1-anilinonaphthalene-8-sulfonic acid; CD, circular dichroism; GdnHCl, guanidine hydrochloride; MRE, mean residue ellipticity; NATA, N-acetyl-l-tryptophanamide; SBD, starch binding domain; Trp, tryptophan; Tyr, tyrosineGlucoamylase; Acid denaturation;
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Formation of molten globule-like state during acid denaturation of Aspergillus niger glucoamylase
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Publisher
Database: Elsevier - ScienceDirect
Journal: Process Biochemistry - Volume 47, Issue 5, May 2012, Pages 775–784
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us