Involved in GM1/GD1B/GA1 ganglioside biosynthesis. ganglioside GM2 (d18:1(4E)) + UDP-alpha-D-galactose = ganglioside GM1 (d18:1(4E)) + H(+) + UDP ganglioside GM2 + UDP-alpha-D-galactose = ganglioside GM1 + H(+) + UDP ganglioside GD2 (d18:1(4E)) + UDP-alpha-D-galactose = ganglioside GD1b (d18:1(4E)) + H(+) + UDP ganglioside GA2 (d18:1(4E)) + UDP-alpha-D-galactose = ganglioside GA1 (d18:1(4E)) + H(+) + UDP Protein modification; protein glycosylation. Highly expressed in thymus, spleen, kidney and testis and, to a lesser extent, in brain and liver. In the embryonic brain, expression begins at day 12 and continues until birth. Expression is maintained at low levels in adult brain. Belongs to the glycosyltransferase 31 family.