Alpha-N-acetylgalactosaminidase complex. Molecular model showing the structure of a molecule of the enzyme alpha-N-acetylgalactosaminidase (yellow) in complex with cofactor NAD + (magenta) and an antigen (purple) from the surface of type A red blood cells. This enzyme has been isolated from bacteria and is capable of stripping the surface of human red blood cells, removing the receptors responsible for creating the blood type. It is being used to develop a technique to produce red blood cells that will be accepted by anyone, regardless of their blood type.