Amino acids produce ammonia through a two-step process involving transamination and oxidative deamination, with a crucial role played by the amino acid glutamate.
Steps in Ammonia Production from Amino Acids
Here’s a breakdown of the process:
- Transamination:
- Most amino acids undergo a process called transamination. During transamination, the amino group (-NH2) from an amino acid is transferred to a keto acid.
- This process creates a new amino acid, commonly glutamate, and a new keto acid.
- The specific keto acid involved in this reaction is often α-ketoglutarate, converting it into glutamate.
- Oxidative Deamination:
- Glutamate is the only amino acid that directly undergoes oxidative deamination.
- In this process, glutamate is stripped of its amino group (-NH2), releasing it as free ammonia (NH3).
- This reaction also regenerates α-ketoglutarate, which can participate in further transamination.
- The free ammonia is then processed to form urea in the liver, which is then excreted from the body.
The Role of Glutamate
The reference highlights the crucial role of glutamate:
- "The amino acid is transaminated to produce a molecule of glutamate. Glutamate is the one amino acid that undergoes oxidative deamination to liberate free ammonia for the synthesis of urea."
- Glutamate acts as a collector of amino groups from other amino acids.
- It is the key intermediate which is deaminated to release free ammonia which is then converted to urea.
Transfer of Ammonia to the Liver
- The reference also clarifies that after ammonia is produced in peripheral tissues, it's not immediately disposed of:
- "Once free ammonia is formed in peripheral tissues, it must be transferred to the liver for the conversation to urea."
- This transfer is necessary for the safe removal of ammonia because ammonia is toxic to cells.
Summary
The process of ammonia production from amino acids can be summarized in the table below:
| Step | Description | Key Molecule |
|---|---|---|
| Transamination | Most amino acids transfer their amino groups to a keto acid, commonly α-ketoglutarate, forming a new amino acid, which is often glutamate. | Glutamate |
| Oxidative Deamination | Glutamate undergoes deamination, releasing ammonia. | Glutamate |
| Ammonia Transfer | Free ammonia is transported to the liver for urea synthesis. | Ammonia |
Thus, while many amino acids participate indirectly, glutamate plays the central role in the actual release of free ammonia.
