Document Detail

Aldehyde Stress-Mediated Novel Modification of Proteins: Epimerization of the N-Terminal Amino Acid.
MedLine Citation:
PMID:  24299224     Owner:  NLM     Status:  Publisher    
Various kinds of aldehyde-mediated chemical modifications of proteins have been identified as being exclusively covalent. We report a unique noncovalent modification: the aldehyde-mediated epimerization of the N-terminal amino acid. Epimerization of amino acids is thought to cause conformational changes that alter their biological activity. However, few mechanistic studies have been performed, because epimerization of an amino acid is a miniscule change in a whole protein. Furthermore, it does not produce a mass shift, making mass spectrometric analysis difficult. Here, we have demonstrated epimerization mediated by endogenous aldehydes. A model peptide, with an N-terminal l- or d-FMRFamide, was incubated with an endogenous or synthetic aldehyde [acetaldehyde, methylglyoxal, pyridoxal 5'-phosphate (PLP), 4-oxo-2(E)-nonenal, 4-hydroxy-2(E)-nonenal, d-glucose (Glc), 4- or 2-pyridinecarboxaldehyde] under physiological conditions. Each reaction mixture was analyzed by liquid chromatography with ultraviolet detection and/or electrospray ionization mass spectrometry. Considerable epimerization occurred after incubation with some endogenous aldehydes (PLP, 40.6% after 1 day; Glc with copper ions, 6.5% after 7 days). Moreover, the epimerization also occurred in whole proteins (human serum albumin and PLP, 26.3% after 1 day). Tandem mass spectrometric studies, including deuterium labeling and sodium borohydride reduction, suggested that the epimerization results from initial Schiff base formation followed by tautomerization to ketimine that causes the chirality to be lost. This suggests that the epimerization of the N-terminal amino acid can also occur in vivo as a post-translational modification under a high level of aldehyde stress.
Ryo Kajita; Takaaki Goto; Seon Hwa Lee; Tomoyuki Oe
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2013-12-3
Journal Detail:
Title:  Chemical research in toxicology     Volume:  -     ISSN:  1520-5010     ISO Abbreviation:  Chem. Res. Toxicol.     Publication Date:  2013 Dec 
Date Detail:
Created Date:  2013-12-4     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8807448     Medline TA:  Chem Res Toxicol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Department of Bioanalytical Chemistry, Graduate School of Pharmaceutical Sciences, Tohoku University , Aobayama, Aoba-ku, Sendai 980-8578, Japan.
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