Glutamic acid constitution

Several of the 20 amino acids that constitute the building blocks of proteins exhibit charged side chains. At pH 7.0, aspartic and glutamic acids have overall negatively charged acidic... 

A series of 1-aminoalkanediphosphonic acids has been reported by the treatment of the N-phenylthiourea derivatives of a>-diethoxyphos-phinoylaldehydes with triphenyl phosphite.343 This constitutes an approach toward the analogues of aspartic and glutamic acid in which both carboxylate sites have been replaced by phosphonic acid functions. A similar approach has also been reported to be of use for the preparation of (diphenyl ester) phosphonate analogues of ornithine, lysine, and homolysine.344345... 

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. 

Carboxylic group—for example, aspartic acid (D) and glutamic acid (E), which provide anionic charges on the surface of proteins and constitute catalytic residues of glycosidases. 

In all the 7-glutamyl peptides reported glutamic acid residues linked via the 7-carboxyl groups have the a-carboxyl free and therefore do not constitute branching points or cross-links. 

Folic acid is a pteridine derivative (rings A and B constitute the pteridine heterocyclic system) synthesized by bacteria from GTP, p-aminobenzoic acid, and glutamic acid. Accordingly. the structure of folic acid is compased of three moieties the pteridine moiety derived from GTP. the p-aminobcnzoic acid moiety, and the glutamic acid moiety. (Antibacterial sulfonamides [see Chapter 8 compete with p-aminobenzoic acid and, thereby, interfere with bacterial folic acid synthesis.) Humans cannot synthesize folic acid. 

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