Glutamine peptides

Steijns, J. 1996. Dietary proteins as the source of new health promoting bio-active peptides with special attention to glutamine peptide. Food Technol. Eur. 3, 80-84. 

Melville, J. Labile glutamine peptides, and their bearing on the origin of the ammonia set free during the enzymic digestion of proteins. Biochem. J. 29, 179 (1935). 

Fukawa, H. Changes of glutamine-peptides on heating in aqueous media. J. Chem. Soc. Jpn. 88 459-463, 1967. 

The phenolic hydroxyl group of tyrosine, the imidazole moiety of histidine, and the amide groups of asparagine and glutamine are often not protected in peptide synthesis, since it is usually unnecessary. The protection of the hydroxyl group in serine and threonine (O-acetylation or O-benzylation) is not needed in the azide condensation procedure but may become important when other activation methods are used. 

Automated ammo acid analysis of peptides containing asparagine (Asn) and glutamine (Gin) residues gives a peak corresponding to ammonia Why" ... 

It is a peptide containing 27 amino acid residues containing the amino acids L-histidine (His) L-aspartic acid (Asp) L-serine (Ser) glycine (Gly) L-threonine (Thr) L-phenyl-alanine (Phe) L-glutamic acid (Glu) L-glutamine [Glu(NHj)] L-leucine (Leu) L-arginine (Arg) L-alanine (Ala) and L-valinamide (Va -NHj). 

An alternative to modifying the functional group attached to fibrils is to utilise the chemistry present in the amino acid side chains. Furthermore, as peptides often undergo specific modification by enzymes in vivo, these could be harnessed for synthetic purposes. Qll (Ac-QQKFQFQFEQQ-Am, a fibril-forming peptide based on Pi 1-2), was coupled to lysine-based molecules by treatment with an enzyme (tissue transglutaminase, TGase) which results in a reaction between lysine and glutamine side chains [72] (Fig. 32). 

Solid state 13C CPMAS NMR spectra of Wheat High Molecular Weight (W.HMW) subunits show well resolved resonances identical with spectra of dry protein and peptide samples [24], Most of the amino acids side-chain resonances are found in the 0-35 ppm region followed by the alpha resonances of the most abundant amino acids glycine, glutamine and proline at chemical shifts of 42, 52 and 60 ppm, respectively, and the carbonyl carbons show a broad peak in 172-177 ppm region. The CPMAS spectra of hydrated whole HMW provides important information on the structural characteristics. 

Rasmussen LK, Sorensen ES, Petersen TE, Gliemann J, Jensen PH. Identification of glutamine and lysine residues in Alzheimer amyloid beta A4 peptide responsible for transglutaminase-catalysed homopolymerization and cross-linking to alpha 2M receptor. FEBS Lett 1994 338 161-166. 

T. P. Creamer (unpublished results). A plot of estimated (ASA) against %PPII content is given in Figure 5. At first glance, it would appear that there is little correlation between the two properties. However, three residues—proline, glycine, and glutamine—can be considered outliers, each for a specific reason. Proline has a high %PPII content in the polyproline-based host peptide used by Kelly et al. (2001) as a result of its unique properties as an imine. As discussed above, a proline that is followed in sequence by a second proline is restricted to the PPII conformation by steric interactions. 

Fig. 6. Ramachandran plots for simulated Ac-Ala-Xaa-Ala-Ala-NMe peptides with Xaa = glutamine or asparagine, with a constrained side chain-to-backbone hydrogen bond. Conformational distribution for glutamine i (A) and for the residue i +1 to which the glutamine is hydrogen-bonded (B). Conformational distribution for asparagine i (C) and for the residue i +1 to which it is hydrogen-bonded (D).

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