Document Detail

Aspartate-induced aminoacylase folding and forming of molten globule.
MedLine Citation:
PMID:  12824065     Owner:  NLM     Status:  MEDLINE    
Aspartate is an osmolyte found in some marine invertebrates and cyclostome fish. The aspartate-induced unfolding of N-acylamino acid amido hydrolase (aminoacylase) has been studied by measuring enzyme activity, fluorescence emission spectra, 8-anilino-1-naphthalenesulfonate (ANS) fluorescence spectra and far-UV circular dichroism (CD) spectra. The results showed that aspartate caused the inactivation and unfolding of aminoacylase. Surprisingly, increasing concentration of aspartate showed the "acid-induced folding", which used to be seen only in strong acids or salts at much lower pH. Although aspartate has the pI of 2.77 that is the lowest among all the free amino acids, it is actually a weak acid. It is thus of great interest why it causes this phenomenon to happen. The relative change of intrinsic fluorescence and ANS binding spectra have shown that there existed a stable molten globule state of aminoacylase with slightly disrupted tertiary structure and more hydrophobic surface. The molten globule state indicates that intermediates existed during aminoacylase refolding process. Unlike the other acids, such as trichloroacetic acid, there is no precipitation observed as the aspartate concentrations increased. It suggests the aspartate anions have an osmotic effect for the molten globule formed during unfolding process. Binding of aspartate anion to the protonated protein, which minimizes the intramolecular repulsion, might explain the osmotic effect of this amino acid in the nature. The results also showed the Apo-aminoacylase followed similar rules as Holo-enzyme, which suggested the zinc ion may play more important roles on activity other than structure.
Qiang Xie; Tai Guo; Tingting Wang; Jie Lu; Hai-Meng Zhou
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The international journal of biochemistry & cell biology     Volume:  35     ISSN:  1357-2725     ISO Abbreviation:  Int. J. Biochem. Cell Biol.     Publication Date:  2003 Nov 
Date Detail:
Created Date:  2003-06-25     Completed Date:  2004-06-08     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  9508482     Medline TA:  Int J Biochem Cell Biol     Country:  England    
Other Details:
Languages:  eng     Pagination:  1558-72     Citation Subset:  IM    
Department of Biological Sciences and Biotechnology, Tsinghua University, Beijing 100084, PR China.
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MeSH Terms
Amidohydrolases / chemistry*,  metabolism
Anilino Naphthalenesulfonates
Apoproteins / chemistry,  metabolism
Aspartic Acid / chemistry,  pharmacology*
Circular Dichroism
Hydrogen-Ion Concentration
Kidney / enzymology
Protein Denaturation / drug effects
Protein Folding*
Salts / pharmacology
Spectrometry, Fluorescence
Reg. No./Substance:
0/Anilino Naphthalenesulfonates; 0/Apoproteins; 0/Salts; 56-84-8/Aspartic Acid; 63741-13-9/5,5'-bis(8-(phenylamino)-1-naphthalenesulfonate); EC 3.5.-/Amidohydrolases; EC I

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