Is there more to learn about functional vitamin D metabolism?

The state of information on the enzymes responsible for the conversion of vitamin D3 to 1α,25-dhydroxyvitamin D3 (1,25-(OH)2D3), the metabolic active form responsible for the well-known function of vitamin D on calcium metabolism and bone mineralization has been briefly reviewed. There remains an unidentified enzyme responsible for 25% of the 25-hydroxylation of vitamin D3, while 75% of serum 25-hydroxyvitamin D3 (25-OH-D3) arises from CYP2R1....