GLT25D2 is a 626 amino acid protein that localizes to endoplasmic reticulum lumen and belongs to the glycosyltransferase 25 family. Possessing beta-galactosyltransferase activity, GLT25D2 transports beta-galactose to hydroxylysine residues on collagen but lacks glucosyltransferase activity. GLT25D2 is expressed in skeletal muscle and brain, and is encoded by a gene located on human chromosome 1q25.3, a region associated with the hereditary prostate cancer (HPC1) locus. Human chromosome 1 spans 260 million base pairs, contains over 3,000 genes, comprises nearly 8% of the human genome and houses a large number of disease-associated genes, including those that are involved in familial adenomatous polyposis, Stickler syndrome, Parkinson’s disease, Gaucher disease, schizophrenia and Usher syndrome.