Basement membrane-associated chondroitin sulfate proteoglycan (CSPG). Has prolyl 3-hydroxylase activity catalyzing the post-translational formation of 3-hydroxyproline in -Xaa-Pro-Gly- sequences in collagens, especially types IV and V. May be involved in the secretory pathway of cells. Has growth suppressive activity in fibroblasts. 2-oxoglutarate + L-prolyl-[collagen] + O2 = CO2 + succinate + trans-3-hydroxy-L-prolyl-[collagen] Secreted into the extracellular matrix as a chondroitin sulfate proteoglycan (CSPG). O-glycosylated; chondroitin sulfate. The disease is caused by variants affecting the gene represented in this entry. A splice site mutation leading to the absence of isoform 1 has been reported in 2 OI8 patients. Isoform 1 is the only form predicted to be located in the endoplasmic reticulum, which the appropriate location for the catalysis of collagen hydroxylation. These patients show indeed severely reduced COL1A1 hydroxylation (PubMed:19088120). Belongs to the leprecan family. Extended N-terminus. Truncated N-terminus. Prolyl 3-hydroxylase 1 (LEPRE1)