| Compound | Description |
|---|
| gamma-aminobutyric acid | The most common inhibitory neurotransmitter in the central nervous system. |
| spermine | A biogenic polyamine formed from spermidine. It is found in a wide variety of organisms and tissues and is an essential growth factor in some bacteria. It is found as a polycation at all pH values. Spermine is associated with nucleic acids, particularly in viruses, and is thought to stabilize the helical structure. |
| 4-aminobutyraldehyde | |
| Spermidine | A polyamine formed from putrescine. It is found in almost all tissues in association with nucleic acids. It is found as a cation at all pH values, and is thought to help stabilize some membranes and nucleic acid structures. It is a precursor of spermine. |
| putrescine | A toxic diamine formed by putrefaction from the decarboxylation of arginine and ornithine. |