The most likely explanations for such increases in ammonia with prepared hemolysates are freezing and aging, which lead to increased ammonia production via deamidation
of the cellular proteins in the hemolysate.
We were able to show that the deamidation
process turns peptide-2 into a relevant epitope for IgG and IgA, whereas the same happened only for IgG in peptide-1.
On the other hand, in one study of Hb Redondo, deamidation
reportedly occurred rapidly in vitro, and after a few days of storage at 4[degrees]C the relative proportions of the two fractions changed (19).
An enzymatic approach to protein deamidation
has advantages over a chemical approach, including speed of reaction.
A possible explanation for the divergent results obtained with different antisera could be that partial deamidation
of asparagine and/or glutamine residues takes place in the degradation products in the acidic conditions used for chromatography.
Robinson does occasionally publish research articles in an obscure area concerning deamidation
rates of asparagine and glutamine in peptides.
Posttranslational modifications of PRL have also been reported: glycosylation in most species; phosphorylation in rats, bovines and birds; deamidation
in rats, mice, sheep and humans and sulfation in ovine or sheep and buffalo (16).
To improve the solubility of WG in milk replacers, deamidation
by acid or alkali treatments, sulfuric, phosphoric or chlorosulfonic acids, or enzymatic hydrolysis by papain, bromelain, subtilisin, trypsin or pronase have been introduced (Day et al.
More recently, it has been discovered that antigliadin antibodies from celiac patients specifically recognize gliadin peptides after deamidation
Some other topics examined are changes in antioxidative properties of lactoglobulin preparation induced by age-related deamidation
, biologically active peptides obtained from food proteins, and organic and transgenic soy and their effects when used in place of animal protein in infancy and old age in rats.
Proteins are susceptible to various forms of destabilizing events including chemical destabilization causing deamidation
, oxidation, and disulfide bond scrambling; and physical destabilization resulting from protein aggregation and precipitation.
This modification has recently been identified as a deamidation
of the glutamine residue at position 63 of Rho to a glutamic acid.