Hi John
The mechanism is stated in references to likely to go via a similar route
as Asn deamidation. In real proteins the 3D structure could likely enhance
the rate of deamidatation by internal sidechain catalysis.
Regarding bulky chains, these affect the deamidation rates of NX in the
following order (as studied by peptides)
G,H,S,D,A,R,L,T,I,V,P: 1,4,8,11,12,13,41,41,57,72,72
Some selected references in the topics related to Gln/Asn on above issues
are:
(Not recent references since I am not updated in the topic, but they
probably still are valid):
Bischoff R and Kolbe HVJ (1994) Deamidation of asparagine and glutamine
residues in proteins and peptides: structural determinants and
analytical methodology. J Chrom B, 662, 261-278.
Clarke SC, Stephensson RC and Lowenson JD (1992) Lability of asparagine and
aspartic acid residues in proteins and peptides. Spontaneous deamidation
and isomerization reactions, in Stability of pharmaceuticals. Part A,
Chemical and physical pathways of protein degradation. (Eds Ahern TJ
and Manning MC Plenum Press, New York and London, Pharmaceutical
Biotechnology, 2,) 1-29
Robinson AB and Robinson LR (1991) Distribution of glutamine and asparagine
residues and their near neighbours in peptides and proteins. Proc Natl
Acad Sci USA, 88, 8880-8884
Liu DT-H (1992) Deamidation: a source of microheterogeneity in
pharmaceutical proteins. TIBTECH, 10, 364-369
Tyler-Cross R and Schricht V (1991) 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(25) 22549-22556
Wright HT (1991) Sequence and structure determinants of the nonenzymatic
deamidation of asparagine and glutamine residues in proteins. Prot Eng,
4(3), 283-294.
Hope this help
I you dig further into the literature I guess you will find more and
fresher studis
Erland Holmberg
Amersham Pharmacia Biotech
John Harlan <john.e.harlan@abbott.com>@aecom.yu.edu> on 2000-11-01 21:53:12
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Subject: ProtChem
I am interested in finding out more about de-amidation. The preliminary
look
I have had in the literature suggests that this primarily occurs in
proteins
in flexible regions with -Asn-Gly- or -Asn-Ser- sequences. A succinimide
intermediate is proposed, which then collapses about 75% to iso-aspartic
acid
and about 25% to aspartic acid. Similar reactions are noted for -Asp-Gly-
and/ -Asp-Ser- sequences.
It is also suggested that -Gln- can undergo this reaction. Are the same
following residues (Ser/Gly) implicated? What is the proposed
intermediate?
Is there any precidence for this type of reaction to occur in sequences
like
-G-N-X-, where X is bulky?
Any facts or lore regarding this would be greatly appreciated.
John Harlan
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