FUT2

This gene encodes α1,2-fucossyltransferase 2 (FUT2). In the ABO blood type, type O antigen (H antigen) is synthesized by the α1,2-FUT group, which transfers fucose to the Gal residue of Galβ1-3/4GlcNAcβ-R structure with α1-2-linkage. This enzyme is one of the three enzymes with α1,2-FUT activity known in human. This enzyme is also known as “Se enzyme”, and is mainly expressed in intestinal epithelium cells, but not expressed in myeloid cells or neuron. In the Bombay phonotype, the activity of both H enzyme (FUT1) and Se enzyme (FUT2) is lost, and the H antigen (O antigen) is not present in the erythrocyte surface nor secretory fluids. In the para-Bombay type, the H antigen is inactivated but the Se antigen has activity; therefore, the H antigen is not synthesized on the erythrocyte surface, but expressed in the intestinal tissue.