A molecular model of the enzyme alpha 1,3 galactosyl transferase with lactose, UDP and a manganese atom binding to the active site. This molecule catalyses the addition of the sugar, 1,3-galactose onto other sugars on the surface of many animal cells. Humans do not have this enzyzme and therefore do not have this sugar on their cells. If the human body encounters cells with 1,3 galactose on their surface it will recognise them as foreign and attack them. This has implications for the use of animal organs as a source of donor material for humans. Research is underway with the aim of producing transgenic pigs that lack this enzyme. These animals will therefore not be able to produce 1,3-galactose and their organs will be less prone to rejection when transplanted into humans.
