This gene encodes α1,2-fucossyltransferase 1 (FUT1). In the ABO blood 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 “H enzyme”, and is broadly expressed in organs of entire body such as myeloid cells, nerve tissue, and intestinal epithelium cells. The H enzyme synthesizes the H antigen on erythrocytes. Rare phenotypes (one in several hundred thousand persons) lacking the H enzyme are called Bombay or para-Bombay phenotypes.
This page does not indicate all of the enzymatic reaction, and expression of "FUT1".