Vitamin D from the skin or diet is metabolized primarily in the liver to 25-hydroxyvitamine D3. What is the rate limiting enzyme in Vitamin D synthesis?

Vitamin D from the skin or diet is metabolized primarily in the liver to 25-hydroxyvitamine D3. 25D is the 'storage' form of vitamin D and is used to determine the vitamin D status of individuals. The last and rate limiting step in the synthesis of 'active' 1,25D is catalyzed by the mitochondrial enzyme 1 hydroxylase and is conventionally known to take place in kidneys.