Amines nonprotein

The nonprotein amino acid /3-A -methylamino-L-alanine (BMAA) is a neurotoxin found in various species of marine cyanobacteria. This nonprotein amino acid occurs both as a free amino acid and bound to proteins.Siderophores are secondary metabolites generally produced by bacteria under iron-deficient conditions. These molecules sequester and transport ferric ion via active transport in bacteria. Some known siderophores are nonribosomal peptides that contain nonprotein amino acids with terminal amines or hydroxylamine side chains, such as exochelin Many of the known nonprotein amino... 

Other nonprotein molecules, such as nucleic acids and oligonucleotides, may not normally possess primary amines of sufficient nucleophilicity to react with common modification reagents. The ability to add amine functional groups to these molecules is sometimes the only route to successful conjugation. Creating amines at specific sites within these molecules allows for site-directed modification at known positions, thus better ensuring active conjugates once formed. 

As indicated in Fig. 1 the two-dimensional area is divided into parts for acidic amino acids, neutral amino acids, basic amino acids and amines. This simple rule holds true not only for the protein amino acids but for a large number of nonprotein amino acids. 

Structurally, the 20 amino acids found in proteins are a-amino carboxylic acids (see Figure 9.1), differing only in their side chains (R groups, see Table 9.1) with the exception of proUne which is an a-imino, carboxylic acid. Some other nonprotein amino acids, however, only vary as to the location of the amine group, e.g., GABA, a y-amine. Others may not even be a carboxylic acid taurine, an amino acid important in the production of bile, is a p-amino sulfonic acid (see Figure 9.2)... 

Nonprotein nitrogen (NPN) compounds are found mostly in the fiber sarcoplasm and include free amino-acids, peptides, amines, amine oxides, guanidine compounds, quaternary ammonium molecules, nucleotides, and urea (Table 6). NPN compounds account for a relatively high percentage of the total nitrogen in the muscles of some aquatic animals, 10-20% in teleosts, about 20% in crustaceans and molluscs, and 30-40% (and in special cases up to 50%) in elasmobranchs. In contrast, NPN compounds in land animals usually represent no more than 10% of total nitrogen. 

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