Disorders in amino acid metabolism

Amino acids are vital substances without which our metabolism cannot assemble proteins. In addition, they have other indispensable tasks, such as those in the nervous system, liver metabolism, growth, or the structure of skin, hair, and nails. The human organism can produce some amino acids, while others must be supplied with food.

Enzymopathie

The processes involved in building up and breaking down amino acids and proteins in the organism are very complex; a whole range of enzymes and coenzymes are involved. If individual ones are defective or are not produced by the body at all or only in insufficient quantities – collectively referred to as enzymopathy – the result is, for example, a disturbance in the amino acid metabolism or diseases such as porphyria or Fabry disease.

The faults at a glance

Defects in amino acid metabolism usually manifest when the precursors or intermediate products cannot be converted into the final amino acid. The result is that these accumulate in the body, but the amino acid is missing or insufficient to fulfil its function. This leads to tissue and organ damage by the intermediate products and failures due to the deficiency of amino acids. 

In some cases, the transport of amino acids is disturbed so that they can no longer be absorbed from the urine and transported back into the body, for example.

The amino acid metabolism disorders have one thing in common: They are based on a congenital gene defect, i.e., inherited. However, most are very rare. The expression can vary – depending on whether an enzyme is completely missing or has a limited function. 

Diagnosis often difficult

Since a metabolic pathway comprises several stations that require different enzymes, several disorders can occur in each case. The path to diagnosis is an odyssey for many of the disorders – since most of these diseases are rare and the symptoms are somewhat non-specific, most doctors do not know too much about them, and the diseases are challenging to recognize.

Exceptions are phenylketonuria and – in Bavaria – urea cycle defects since screening tests have already been carried out for these in newborns, and they are thus recognized at an early stage. The therapeutic spectrum is also often quite limited – in the case of rare clinical pictures, intensive research is hardly worthwhile for pharmaceutical companies.