Multifunctional enzyme that catalyzes a series of essential post-translational modifications on Lys residues in procollagen (  ). Plays a redundant role in catalyzing the formation of hydroxylysine residues in -Xaa-Lys-Gly- sequences in collagens (   ). Plays a redundant role in catalyzing the transfer of galactose onto hydroxylysine groups, giving rise to galactosyl 5-hydroxylysine ( , ). Has an essential role by catalyzing the subsequent transfer of glucose moieties, giving rise to 1,2-glucosylgalactosyl-5-hydroxylysine residues (   ). Catalyzes hydroxylation and glycosylation of Lys residues in the MBL1 collagen-like domain, giving rise to hydroxylysine and 1,2-glucosylgalactosyl-5-hydroxylysine residues . Essential for normal biosynthesis and secretion of type IV collagens  (Probable). Essential for normal formation of basement membranes (By similarity).
Subcellular locations: Rough endoplasmic reticulum, Endoplasmic reticulum lumen, Endoplasmic reticulum membrane, Secreted, Secreted, Extracellular space
The majority of the secreted protein is associated with the extracellular matrix.
Ubiquitous . Detected in heart, placenta and pancreas and at lower levels in lung, liver and skeletal muscle (, ).