Alpha-galactosidase is an enzyme that has variable activity depending upon the species of origin. In humans, the most well known form of the enzyme is alpha-galactosidase A, which catalyzes a hydrolysis reaction to remove a specific monosaccharide, or simple sugar, from a specific glycolipid, or molecule made up of both sugar and fat. In addition to the human form of alpha-galactosidase, the dietary supplement Beano contains an alpha-galactosidase derived from a fungus.
Significance
Human alpha-galactosidase performs a reaction that normally occurs within the lysosome, an organelle within the cell that is responsible for the breakdown of many biomolecules. The enzyme breaks apart a sugar-fat complex that can otherwise accumulate in cells, explain Drs. Reginald Garrett and Charles Grisham in their book, "Biochemistry." If alpha-galactosidase isn't present or fails to function, the partially digested sugar-fat complex, known as globotriaosylceramide, accumulates in a variety of tissues including the lining of the blood vessels, kidneys, heart, and nervous tissue.
Effects
In research, enzymes can be characterized in two ways--by their effects, and by the resulting diseases that occur if the enzymes are deficient or absent. The absence of alpha-galactosidase results in a condition known as Fabry's disease. The symptoms of Fabry's disease usually begin in the first or second decade of life and include a burning sensation in the hands and widespread red to purple colored blemishes on the skin that are 1-5 mm in diameter. Kidney effects initially present with proteinuria, or excessive excretion of serum proteins and eventually progress to renal insufficiency followed by possible renal failure. Effects upon the heart generally display an increased risk of heart disease, note Drs. Garrett and Grisham.
Supplementation
Humans deficient in alpha-galactosidase who have Fabry's disease are treated with a supplement of alpha-galactosidase A. There are two different enzyme replacement therapies available, marketed under the names Replagal and Fabrazyme. Both of these therapies contain forms of human alpha-galactosidase A. The enzymes have been modified with various sugars to prevent degradation by proteins in the bloodstream. Fabrazyme, the trade name for agalsidase-beta, is available in the US while Replagal, the trade name for agalsidase-alpha, is still waiting for FDA approval, notes the website FDA News. Both therapies must be administered every two weeks to be effective.
Misconceptions
Humans also benefit from enzymes derived from other sources. For instance, the dietary supplement Beano contains an alpha-galactosidase derived from a fungus, and yet many humans benefit from supplementation with the fungal enzyme. The alpha-galactosidase found in Beano is meant to degrade complex sugars such as raffinose that are found in foods such as beans, broccoli and some whole grains. In the case of raffinose, alpha-galactosidase catalyzes a hydrolysis reaction to convert raffinose into the simple sugar galactose and common table sugar, sucrose, explain Drs. Mary Campbell and Shawn Farrell in their book, Biochemistry."
Expert Insight
Since humans normally lack intestinal activity of alpha-galactosidase, ingested raffinose is usually not absorbed from the diet and instead passed into the large intestine where it is metabolized, or digested by bacteria. This produces a variety of by-products including carbon dioxide, hydrogen and methane that are responsible for the flatulence caused by eating foods containing raffinose and related sugars. While it isn't meant to treat medical conditions, the use of a product such as Beano can provide alpha-galactosidase to allow for the digestion of sugars such as raffinose and prevent the intestinal fermentation of these sugars, note Drs. Campbell and Farrell. As such, alpha-galactosidase supplementation in the diet may make consumption of certain foods more comfortable.
References
- "Biochemistry"; Reginald Garrett, Ph.D. and Charles Grisham, Ph.D.; 2007
- FDA News: Replagal
- "Biochemistry"; Mary Campbell, Ph.D. and Shawn Farrell, Ph.D.; 2005
