Reaction catalyzed by EGF-domain serine xylosyltransferase (2.4.2.63)

		+		[Notch1 protein with EGF-like domain 12]-L-serine	=			+		[Notch1 protein with EGF-like domain 12]-3-O-(beta-D-xylosyl)-L-serine
	UDP-alpha-D-xylose	+		[Notch1 protein with EGF-like domain 12]-L-serine	=		UDP	+		[Notch1 protein with EGF-like domain 12]-3-O-(beta-D-xylosyl)-L-serine