Putrescine

Putrescine is an organic compound with the chemical formula (CH2)4(NH2)2. It is a colorless solid that melts near room temperature. Scientists classify it as a diamine, which is a type of molecule containing two amine groups. While many people recognize it by its foul odor, it is a vital part of life. Putrescine is found in all living organisms. It plays many different roles in the biology of plants, animals, and even humans.

In living cells, putrescine is created through two distinct biological pathways. Both pathways begin with the amino acid arginine. In the first pathway, an enzyme called arginine decarboxylase (ADC) converts arginine into agmatine. Next, an enzyme known as agmatine imino hydroxylase (AIH) transforms agmatine into N-carbamoylputrescine. Finally, this substance is hydrolyzed to produce putrescine. The second pathway is different. In this route, arginine is first converted into ornithine. Then, an enzyme called ornithine decarboxylase (ODC) turns that ornithine into putrescine.

Once it is made, putrescine can be used to build even more complex molecules. It serves as a building block for other polyamines. For example, the enzyme spermidine synthase combines putrescine with S-adenosylmethioninamine to create spermidine. This spermidine can then be combined with another S-adenosylmethioninamine to produce spermine.

This process is a key part of how cells manage their internal chemistry.

Putrescine also plays a significant role in the brain. It can act as a biological precursor for gamma-aminobutyric acid, or GABA. GABA is a chemical that helps regulate the brain. Putrescine can be transformed into GABA through various intermediates, such as N-acetylputrescine and GABAL. These changes are managed by enzymes like diamine oxidase (DAO) and monoamine oxidase B (MAO-B). In 2021, researchers discovered that MAO-B helps synthesize GABA in astrocytes. This happens in several brain areas, including the hippocampus, cerebellum, striatum, cerebral cortex, and the substantia nigra pars compacta. This synthesized GABA then works to inhibit certain dopaminergic neurons.

In the world of plants, putrescine is often the most common polyamine found in tissues. It helps plants manage stress from the environment, such as heat or drought. It can also act as a regulator for proteins on cell surfaces and inside organelles like mitochondria and chloroplasts. For instance, an increase in putrescine can lead to higher ATP production in these parts of the cell. However, it can also act as a developmental inhibitor. In Arabidopsis plants, high levels can cause dwarfism or late flowering. Without enough putrescine, plants may also see an increase in fungal and parasite populations.

Farmers and scientists use putrescine in interesting ways to help agriculture. When applied to fruits like peaches, plums, or pears, it can delay the ripening process. This extends the shelf life of the produce. In one study, a strawberry coating made of putrescine and chitosan helped the fruit stay fresh for up to 12 days. It also helps fruits keep their firmness, taste, and nutrition. In the soil, a fungus called Piriformospora indica can promote putrescine production in tomato and Arabidopsis plants. This helps the plants grow better root structures.

Beyond biology, putrescine has important industrial and historical uses. In factories, it is produced on an industrial scale through the hydrogenation of succinonitrile. It can also react with adipic acid to create nylon 46, a material sold as Stanyl. Historically, the substance was first described in 1885 by Ludwig Brieger. He was a physician from Berlin. He named the compound "putrescine" from the Latin word *putresco*, which means to become rotten or decay. Because it is found in decaying flesh alongside cadaverine, it is often used as a biochemical marker to help determine how long a corpse has been decomposing.