Ultraviolet-B induced photoconversion to vitamin D3

The "Ultraviolet-B induced photoconversion to vitamin D3" refers to the process by which **7-dehydrocholesterol**, present in the skin, absorbs ultraviolet B (UVB) radiation (wavelengths 280–315 nm), leading to the cleavage of the B ring in the sterol and formation of **previtamin D3**. Previtamin D3 spontaneously isomerizes (thermally) to form **vitamin D3** (cholecalciferol), which is subsequently released into the circulation. This process is critical for maintaining adequate vitamin D levels and, consequently, calcium and phosphate balance in vertebrates, including humans. The pathway is regulated by physical (skin pigmentation, UV exposure, latitude, age) and physiological factors and is not directly targeted pharmacologically. "Ultraviolet-B induced photoconversion to vitamin D3" describes a *reaction*, not a drug target. The molecule involved is **7-dehydrocholesterol** (provitamin D3), which—under UVB exposure—initiates vitamin D3 synthesis, but this is not considered a receptor, enzyme, or classical therapeutic target.

Other names

Provitamin D3 (for 7-dehydrocholesterol)Cholecalciferol (for Vitamin D3)

Not applicable to a molecule/receptor; vitamin D supplements act by replenishing levels downstream in this pathway. No pharmacological blockade/activation of the process exists.