A glycine

Biosynthesis. Two closely related genes encode the three mammalian tachykinins. The preprotachykinin A gene encodes both substance P and substance K, while the preprotachykinin B gene encodes neuromedin K (45—47). The active sequences are flanked by the usual double-basic amino acid residues, and the carboxy-terrninal amino acid is a glycine residue which is decarboxylated to an amide. As with most neuropeptide precursors, intermediates in peptide processing can be detected, but their biological activities are not clear (ca 1994). 

Glycine residues have more conformational freedom than any other amino acid, as discussed in Chapter 1. A glycine residue at a specific position in a protein has usually only one conformation in a folded structure but can have many different conformations in different unfolded structures of the same protein and thereby contribute to the diversity of unfolded conformations. Proline residues, on the other hand, have less conformational freedom in unfolded structures than any other residue since the proline side chain is fixed by an extra covalent bond to the main chain. Another way to decrease the number of possible unfolded structures of a protein, and hence stabilize the native structure, is, therefore, to mutate glycine residues to any other residue and to increase the number of proline residues. Such mutations can only be made at positions that neither change the conformation of the main chain in the folded structure nor introduce unfavorable, or cause the loss of favorable, contacts with neighboring side chains. 

What is the pH of a glycine solution in which the a-NHj group is one-third dissociated ... 

El fazepam (80) not only is a tranquilizer, but also stimulates feeding in satiated animals. One of several syntheses involves reaction of benzophenone derivative with a glycine equivalent masked as an oxazolidine-2,5-dione (79). ... 

These two selectors terminated with a glycine were then prepared on a larger scale, their carboxyl groups reacted with 3-aminopropyltriethoxysilane, and the conjugate immobilized onto silica. Each CSP was packed into columns and used for the separation of racemic (l-naphthyl)leucine ester 17. Separation factors of 6.9 and 8.0 were determined for the columns with DNB-ala-gly and DNB-leu-gly selector respectively. These were somewhat lower than those found for similar CSPs using the parallel synthesis and attached through a different tether [87]. 

The amidoalkylation of certain allylsilanes with a glycine cation equivalent shows low stereoselectivity 84. 

Moderate stereoselectivity is observed in the reaction of a glycine cation equivalent with a silyl enol ether86. 

Mediocre diastereoselectivity is found on cyclization of a glycine cation equivalent 4,45a. 

For many serine and cysteine peptidases catalysis first involves formation of a complex known as an acyl intermediate. An essential residue is required to stabilize this intermediate by helping to form the oxyanion hole. In cathepsin B a glutamine performs this role and sometimes a catalytic tetrad (Gin, Cys, His, Asn) is referred too. In chymotrypsin, a glycine is essential for stabilizing the oxyanion hole. 

A number of peptide hormones have a carboxyl terminal amide which is derived from a glycine terminal residue. This glycine is hydroxylated on the a-carbon by a copper-containing enzyme, peptidylglycine hydroxylase, which, again, requires ascorbate for reduction of Cu ". ... 

Coschigano PW, TS Wehrman, LY Yonng (1998) Identification and analysis of genes involved in anaerobic tolnene metabolism by strain Tl pntative role of a glycine free radical. Appl Environ Microbiol 64 1650-1656. 

Papoular, R.J., Vekhter, Y. and Coppens, P. (1996) The two-channel maximum-entropy method applied to the charge density of a molecular crystal a-glycine, Acta Cryst., A52, 397 107. 

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