Has a D-25-hydroxylase activity on both forms of vitamin D, vitamin D(2) and D(3). Defects in CYP2R1 are the cause of rickets vitamin D- dependent type 1B (VDDR1B); also known as pseudovitamin D(3) deficiency rickets due to 25-hydroxylase deficiency. A disorder caused by a selective deficiency of the active form of vitamin D (1,25-dihydroxyvitamin D3) and resulting in defective bone mineralization and clinical features of rickets. The patients sera have low calcium concentrations, low phosphate concentrations, elevated alkaline phosphatase activityand low levels of 25-hydroxyvitamin D. Belongs to the cytochrome P450 family. Note: This description may include information from UniProtKB.