Asparagine residues ribonuclease

Ribonuclease from other mammalian sources may have several carbohydrate fragments in their structures. Thus, ribonuclease B from porcine pancreas contains at least three carbohydrate moieties, and these are attached9 at asparagine residues 21, 34, and 76. The carbohydrate moieties present at residues 21 and 76 are considerably more complex than that at residue 34, and their structures are under investigation in several laboratories. The carbohydrate portions of the isoenzymes of deoxyribonuclease are similar in structure to those from the ribonucleases.11 As ribonuclease and deoxyribonuclease originate in the same organ, it is possible that the same pathways and enzymes are utilized for the biosynthesis of the carbohydrate moieties of both enzymes. 

Mizrahi V, Brooksbank RL, Nkabinde NC. Mutagenesis of the conserved aspartic acid 443, glutamic acid 478, asparagine 494, and aspartic acid 498 residues in the ribonuclease H domain of p66/p51 human immunodeficiency vims type 1 reverse transcriptase. JBiol Chem 1994 269 19245-19249. 

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. 

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