Glutamine properties

As a p hydroxy derivative of phenylalanine tyrosine has properties similar to those of phenylalanine plus the ability to engage m hydrogen bonding via its —OH group Asparagine and glutamine are not amines they are amides The side chains of both O... 

Glutamic acid, structure and properties of, 1019 Glutamine, structure and properties of, 1018... 

T. P. Creamer (unpublished results).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. 

A second method of activating the acid for esterification (see Section 7.6) is as the mixed anhydride. The mixed-anhydride reaction had been employed decades ago for preparing activated esters. However, it was never adopted because of its unreliability and the modest yields obtained. The method was fine-tuned (Figure 7.12), after reliable information on the properties of mixed anhydrides was acquired (see Section 2.8). Tertiary amine is required for esterification of the mixed anhydride to occur. The method is generally applicable, except for derivatives of asparagine, glutamine, and serine with unprotected side chains. The base also prevents decomposition that occurs when the activated derivative is a Boc-amino acid (see... 

Glutamine Synthetase of Escherichia coli. Some Physical and Chemical Properties Ann Ginsburg... 

Note that the side-chains of glutamine and asparagine are not basic these side-chains contain amide functions, which do not have basic properties (see Section 4.5.4). The heterocyclic ring in tryptophan can also be considered as non-basic, since the nitrogen lone pair electrons form part of the aromatic jt electrons and are unavailable for bonding to a proton (see Section 11.8.2). 

Especially in the case of high-molecular-weight surface-active substances (such as proteins), the period of change may be sufficiently prolonged to allow easy observation. This arises because proteins are surface active. All proteins behave as surface-active substances because of the presence of hydrophilic-lipophilic properties imparted from the different polar, such as glutamine and lysine, and apolar, such as alanine, valine, phenylalanine, isovaline, amino acids. Proteins have been extensively investigated as regards their polar-apolar characteristics as determined from surface activity. 

Based on the properties of the side chains, the 20 amino acids can be put into six general classes. The first class contains amino acids whose side chains are aliphatic, and is usually considered to include glycine, alanine, valine, leucine, and isoleucine. The second class is composed of the amino acids with polar, nonionic side chains, and includes serine, threonine, cysteine, and methionine. The cyclic amino acid proline (actually, an imino acid) constitutes a third class by itself. The fourth class contains amino acids with aromatic side chains tyrosine, phenylalanine, and tryptophan. The fifth class has basic groups on the side chains and is made up of the three amino acids lysine, arginine, and histidine. The sixth class is composed of the acidic amino acids and their amides aspartate and asparagine, and glutamate and glutamine. 

The ability of enzyme preparations from various animal tissues to catalyze transfer of the glutamyl unit from glutamine or glutathione to certain a-amino acids and peptides, first observed by Hanes et al. (38), has been examined in several laboratories (32, 35, 39-41). Enzymes of this type have been studied recently by Orlowski and Meister (in hog kidney) (32) and by Szewczuk and Baranowski (in beef kidney) (41)-Results with the hog kidney enzyme will be reviewed here the beef enzyme is quite similar in many respects, but it is not identical in physical properties. 

An enzyme possessing the properties of L-glutamine cyclotransferase has not as yet been found in animal tissue. However, the conversion of glutamine to pyrrolidone caboxylic acid by a two-step enzyme-catalyzed pathway has been observed (13). Thus, glutamine may be converted to y-glutamyl glutamine by y-glutamyl transpeptidase ... 

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