AMINES Part 2 - Biogenic Amines

In my previous post, I wrote about four different types of amines which we come across in our everyday life. They are the amino acids, biogenic amines, trymethylamine and aniline.

In this post, I will be writing about the biogenic amines and how it affects our everyday lives.

Biogenic Amines

A biogenic amine is biogenic substance with one or more amine groups. A biogenic substance is a substance which is produced by life processes. It could be secreted or is a part of plants and animals.

Examples of biogenic amines are:

a. Histamine

This is a substance which is derived from the amino acid histidine which acts as a neurotransmitter mediating arousal and attention. It is also a pro-inflammatory signal released from mast cells in response to allergic reactions or tissue damage.

Histamine is also an important stimulant of HCl (hydrochloric acid) secretion by the stomach through the histamine H2 receptors.

b. Serotonin

This is a central nervous system neurotransmitter derived from the amino acid tryptophan. Its role is to regulate mood, sleep, appetite and sexuality.

c. Catecholamine neurotransmitters

There are three of this neurotransmitters:

• Norepinephrine - This is a neurotransmitter which is involved in sleep and wakefulness, attention, feeding behaviour and a stress hormone that regulates the sympathetic nervous system.
• Epinephrine - This is an adrenal stress hormone.
• Dopamine - This is a neurotransmitter that is involved in motivation, reward, addiction, behavioral reinforcement and coordination of body movements.

d. Trace Amines

• 3-Iodothyronamine - This is a metabolite of the thyroid hormones.
• Tryptarmine - This is a monoamine alkaloid found in the brains of mammals. It acts as a neuromodulator and neurotransmitter.
• Tyramine - This is a substance found in many types of common food which causes migraines, headaches and elevated blood pressure.
• Dimethyltryptamine (DMT)
• Phenethylamine
• Octopamine

Two Types of Biogenic Amines

1. Endogenous Biogenic Amines

Endogenous is defined as substances which originate from within an organism, tissue or cell. Endogenous amines are produced in many different tissues within our bodies. Adrenaline is produced in our adrenal medulla and histamine is produced in our mast cells and liver.

2. Exogenous Biogenic Amines

Exogenous is defined as something which is outside the system. In this case, exogenous biogenic amines are amines which are not from our bodies. These are from the food that we eat which are then absorbed into our system via the intestines.

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Monoamine oxidases (MAO) are a family of enzymes in our system which helps break down the amines in our bodies. It also prevents our bodies from excessive amine resorption. Without this family of enzymes, (or a lack of or too much) in our bodies, it can result in psychiatric and neurological disorders. The monoamine oxidase is further divided into two sub-groups: MAO-A and MAO-B.

a. MAO-A

• This is found in the liver, gastrointestinal tract and placenta. This MAO-A is very vital in the catabolism of monoamines which are ingested in food. Catabolism means the molecules are broken down in smaller units to release energy which contributes to wakefulness and maintenance and growth of cells.
• MAO-A mostly breaks down serotonin, melatonin, noradrenaline and adrenaline. 
• Adrenaline/noradrenaline will be turned into 3,4-Dihydroxymandelic acid, which is a hormone and neuron transmitter.
• Metanephrine will be turned into vanillylmandelic acid (VMA) which if is elevated in the urine, the patient would have tumors (adrenal gland tumors) that secrete catecholamines.
• MAO-A inhibitors are used as antidepressants and anti-anxiety agents.

b. MAO-B

• This is found mostly in blood platelets. 
• Dopamine will be turned to dihydroxyphenylacetic acid. This seems to be the trigger for Parkinson's disease. 
• MAO-B inhibitors (sometimes used together with MAO-A inhibitors) are used to treat Alzheimer's and Parkinson's diseases.

Thus, unusually high or low levels of MAOs in the body has been connected to depression, schizophrenia, attention deficit disorder, and even migraines.

Click on LINK to read more about the importance and functions of monoamine oxidase (MAO) in our bodies.