Galactosamine is a carbohydrate, or more specifically, an amino sugar. The name is derived from the words "galactose," which is a monosaccharide sugar, and "amine." Galactosamine is therefore an amino derivative of the sugar galactose. This amino sugar is a major component of glycoproteins, an essential part of living cells. Galactosamine can also be found in small amounts in soil.
Humans and animals do not derive galactosamine from the diet; rather it is synthesized within the body. Galactosamine is a hexosamine, formed when an amino group replaces one of the hydroxy groups of a six-carbon sugar, or hexose. Galactosamine is synthesized in the body from UDP-N-acetyl-D-glucosamine, or glucosamine, and is most often found in the form N-Acetyl-D-galactosamine. This form is also referred to as N-Acetylgalactosamine.
Galactosamine is a constituent of hyaluronic acid, a potent water-binding agent. Hyaluronic acid is found in many types of tissues, including brain, skin and connective tissues. It acts as a lubricating agent in the synovial fluid of joints and in connective tissue. In the eye, hyaluronic acid acts as a lubricating agent in the vitreous humor. Medicine makes use of hyaluronic acid in wound or burn dressings, during cataract or corneal transplantation surgery, as an osteoarthritis treatment and as a plastic surgery aid.
One of the components of chondroitin sulfate is galactosamine. Chondroitin is found in the cornea, lung tissue, bone, blood vessels and connective tissue. It provides both strength and elasticity to cartilage in joints. Chondroitin also helps to absorb water into the connective tissue. As a supplement, chondroitin might help to reduce the pain and swelling of arthritis.
Galactosamine is an element of human glycoproteins. This includes the glycoprotein hormones follicle-stimulating hormone (FSH), chorionic gonadotropin and luteinizing hormone (LH). Glycoproteins are found in immunoglobulins, the infection-fighting proteins also known as antibodies. Proteins found in plasma, the extracellular fluid surrounding cells, are made of glycoproteins. Galactosamine is also a component of the human B-type blood cell.
Some bacterial and fungal cell walls contain galactosamine. The gram-negative enterobacteria, including salmonella and Escherichia coli, contain galactosamine. In these bacteria, it is an important element of the cell wall polysaccharides.
A few amino sugars, including galactosamine, have been shown to kill tumors in the laboratory. It is unlikely to be used in cancer therapy, however. D-galactosamine is a hepatotoxic, or liver-damaging, agent. Researchers studying animal models of liver failure sometimes use D-galactosamine to induce liver damage. Galactosamine is also helpful for researchers studying agents that might protect the liver from damage.