Deamidation of asparagines

R. Tyler-Cross and V. Schirch, Effects of amino acid sequence, buffers and ionic strength on the rate and mechanism of deamidation of asparagine residues in small peptides, J. Biol. Chem, 266, 22549 (1991). 

Figure 6.19 Deamidation of asparagine and glutamine, yielding aspartic acid and glutamic acid respectively. This process can often be minimized by reducing the final product pH to A-5...

R. Bischoff, H. V. J. Kolbe, Deamidation of Asparagine and Glutamine Residues in Proteins and Peptides Structural Determinants and Analytical Methodology , J. Chro-matogr., B 1994, 662, 261-278. 

M. L. Di Salvo, S. Delle Fratte, B. Maras, F. Bossa, H. T. Wright, V. Schirch, Deamidation of Asparagine Residues in a Recombinant Serine-Hydroxymethyltransferase , Arch. Biochem. Biophys. 1999, 372, 271-279. 

L. Takemoto, D. Boyle, Specific Glutamine and Asparagine Residues of yS-Crystallin Are Resistant to in vivo Deamidation , J. Biol. Chem. 2000, 275, 26109 - 26112 L. Takemoto, D. Boyle, Increased Deamidation of Asparagine During Human Senile Cataractogenesis , Mol. Vision 2000, 6, 164-168. 

An enzyme can deactivate irreversibly for two kinds of reasons (i) conformational processes, such as aggregation (intermolecular), or incorrect structure formation (intramolecular), such as scrambled disulfide bond formation between wrong side chains, and (ii) covalent processes, such as reduction and thus destruction of disulfide bonds, deamidation of asparagine (Asn) or glutamine (Gin) side chains, or hydrolysis of (usually) labile asp-X bonds in the protein sequence. 

In a classic study on bovine pancreatic ribonuclease A at 90°C and pH conditions relevant for catalysis, irreversible deactivation behavior was found to be a function of pH (Zale, 1986) at pH 4, enzyme inactivation is caused mainly by hydrolysis of peptide bonds at aspartic acid residues as well as deamidation of asparagine and/or glutamine residues, whereas at pH 6-8, enzyme inactivation is caused mainly by thiol-disulfide interchange but also by fi-elimination of cystine residues, and deamidation of asparagine and/or glutamine residues. 

Aswad DW. Stoichiometric methylation of porcine adrenocorticotropin by protein carboxyl methyltransferase requires deamidation of asparagine 25. Evidence for methylation at the alpha-carboxyl group of atypical L-isoaspartyl residues. J Biol Chem 1984 259 10714-10721. 

Friedman AR, Ichhpurani AK, Brown DM, Hillman RM, Krabill LF, Martin RA, Zurcher-Neely HA, Guido DM (1991), Degradation of growth hormone releasing factor analogs in neutral aqueous solution is related to deamidation of asparagine residues. Replacement of asparagine residues by serine stabilizes, Int. J. Pept. Protein Res. 37 14-20. 

Absolute identification of the modified amino acids may require more than one enzyme digest to produce different peptides. Some kinds of modifications that are easily identified by MS include phosphorylation of threonine or serine sulfation or phosphorylation of tyrosine deamidation of asparagine or glutamine O-or N-linked glycosylation oxidation of methionine or cysteine and N-terminal modification by formylation or prenylation. Combining enzymatic maps (tryptic mapping) with MS/MS may identify single amino acid variants of the protein that cannot otherwise be seen. 

Lindner, H. and W. HeUiger, Age-dependent deamidation of asparagine residues in proteins, Exp. Gerontol., 36,1551-1563, 2001. 

The hydrolytic deamidation of asparagine is catalyzed by the enzyme asparaginase (E.C. 3.5.1.1). This enzyme has been detected in crude extracts of seeds of Lupinus albus (Atkins et al., 1975) and has been purified 470-fold from maturing seeds of Lupinus polyphyllus (Lea et al., 1978). The enzyme has a high for asparagine, but the asparagine concentration in the phloem stream to the developing seed is about 30 mM (Atkins et al., 1975) which is three times the value. 

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