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 secretoty pathway of cells. Has growth suppressive activity in fibroblasts. 2-oxoglutarate + L-prolyl-[collagen] + O2 = CO2 + succinate + trans-3-hydroxy-L-prolyl-[collagen] Binds unfolded collagen in a complex with CYPB and CRTAP. Expressed in embryonic dermis, tendon, cartilage, liver and kidney. Expression in the kidney is restricted to the calyx. In the liver, expression is restricted to the interlobular septum. Belongs to the leprecan family.