The function of ENSG00000173950 (XXYLT1, xyloside xylosyltransferase 1) is as follows. Alpha-1,3-xylosyltransferase, which elongates the O-linked xylose-glucose disaccharide attached to EGF-like repeats in the extracellular domain of target proteins by catalyzing the addition of the second xylose (PubMed:22117070, PubMed:8982869). Known targets include Notch proteins and coagulation factors, such as F9 (PubMed:22117070, PubMed:8982869). {ECO:0000269|PubMed:22117070, ECO:0000269|PubMed:8982869}.