What is alpha-galactosidase?

The alpha-galactosidase is an enzyme that belongs to the group of hydrolases. Another name for the enzyme is ceramide trihexosidase. The enzyme is found in all human cells and splits the alpha-D-glycosidic bond.

An alpha-glycosidic bond is present when a carbohydrate such as galactose is linked to an alcohol group, for example. More precisely, the enzyme alpha-galactosidase occurs in the lysosome of the cells and splits glycosphingolipids and glycoproteins into their individual components. A defect in the enzyme caused by a gene defect can lead to the clinical picture of Fabry’s disease.

Task, function & effect of alpha-galactosidase

Alpha-galactosidase is an enzyme and its task is to help break down special fats. These fats can be absorbed into the body through food. In the body they are found in almost all cells.

The breakdown of fats by alpha-galactosidase prevents pathological proliferation within the cells. The way the enzyme works is similar to that of a classic hydrolysis. During hydrolysis, the chemical bond (alpha-D-glycosidic bond) between the individual components of a molecule is split under the incorporation of a molecule of water, resulting in two products.

Due to the typical property of the enzyme, the reaction of splitting fats is significantly accelerated. As a result, more fats can be broken down per time unit. The enzyme alpha-galactosidase, like all enzymes, emerges from this reaction unchanged and in the same quantity.

The catalyzed reaction of alpha-galactosidase has the effect of reducing the total amount of glycosphingolipids in the body. Glycosphingolipids is the name for the fats that are broken down by alpha-galactosidase. Overall, this prevents the death of the body cells, due to the accumulation of glycosphingolipids in the cells. Thus the clinical picture of Fabry’s disease does not occur.

Where is it made?

Precursors of the enzyme alpha-galactosidase are synthesized by the ribosomes of the cells. These release a chain of amino acids, which later form the finished enzyme, into the endoplasmic reticulum. Here the enzyme matures into the finished enzyme.

From there, the amino acid chains are transported by special vesicles to the Golgi apparatus. From here, the enzymes can either be transported through vesicles into the lysosomes or to the cell surface and released into the space between the cells. Other cells can now take up the enzymes by receptor-mediated absorption.

Alpha-galactosidase decreased

A deficiency of the enzyme alpha-galactosidase results in a reduced breakdown of fats (glycosphingolipids) in the cells of the body. This leads to an accumulation of fats in the lysosomes of the cells. This accumulation is poorly tolerated by most cells and has harmful effects on them.

As a result, programmed cell death often occurs. This can manifest itself in various symptoms such as skin and vessel changes or pain in the hands and feet. Fabry’s disease is a disease caused by a deficiency of alpha-galactosidase.

The cause of the deficiency is usually hereditary and very rare. The disease is often first noticed when several symptoms appear in late childhood. There are punctiform skin changes, pain in the hands and feet, altered temperature sensation, hearing loss, changes in the eyes and protein in the urine.

Due to changes in the vessels, the kidneys are particularly at risk of a renal infarction or renal insufficiency in the course of the disease. The heart is also at risk of a heart attack. A stroke often occurs as well.

The therapy consists of the early substitution of the enzyme with tablets. In the course of the treatment, dialysis or a kidney transplant may become necessary. If there is a deficiency of the enzyme alpha-galactosidase, it can be very well contained by taking tablets, so that hardly any changes are noticeable.

The tablets contain artificially produced enzymes which correspond exactly to the body’s own enzymes in their function. Substitution with tablets is the generally applied therapy for known deficiency of alpha-galactosidase. For this reason the therapy is also called enzyme replacement therapy. Since the cells of the body have special receptors on the surface that recognise the enzyme, the cells can absorb the enzyme into their plasma by endocytosis. After absorption, the enzymes unfold their effect within the cell, which reduces the amount of glycosphingolipids.