2.4.1.B7	C121G	a polymorphic UGT3A1 variant containing a C121G substitution is catalytically inactive	704454	
2.4.1.B7	N391F	residue N391 is necessary for utilization of UDP-GlcNAc as substrate. Mutation N391F in UGT3A1 enhances its ability to utilize UDP-Glc and completely inhibits its ability to use UDP-GlcNAc. An analysis of homology models docked with UDP-sugar donors indicates that N391 in UGT3A1 is able to accommodate the N-acetyl group on C2 of UDP-GlcNAc so that the anomeric carbon atom C1 is optimally situated for catalysis involving residue His35. Replacement of Asn with Phe at position 391 disrupts this catalytically productive orientation of UDP-GlcNAc but allows a more optimal alignment of UDP-Glc for sugar donation	722767