LARGE

This gene is one of the largest gene in human genome, encoding a glycosyltransferase with activity of β1-3-glucuronic acid transferase and 1,3-xylose transferase. This enzyme is related to synthesis of glycan on α−dystroglycan (phosphorylated O-mannose: N-acetylgalactosamine-beta-3-N-acetylglucosamine-beta-4-(phosphate-6-)mannose) by synthesizing the repeating disaccharide unit of (Xyla1-3GlcAb1-3)n. The O-mannose glycan on α−dystroglycan plays an important role for the binding with laminin, which is important in muscle function. It was clarified that mutation of this gene induces abnormal glycosylation of α−dystroglycan and results in MDC1D, one of congenital muscular dystrophy. Transfer reaction of GlcA ([GlcAb1-4Xyla1-R), the origin of the repeating disaccharide unit ([Xyla1-3GlcAb1-4]n) synthesized by LARGE/LARGE2, is related to B4GAT1.