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The conversion of vitamin D, especially cholecalciferol, to 25(OH)D (calcifediol) is one of the key steps in the vitamin D hormonal system. The CYP2R1 enzymatic activity achieving this process was previously thought to be constitutively expressed and stable, so that serum 25(OH)D was a measure of the supply of vitamin D. [9]
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The natural, active form of vitamin D is calcitriol (1,25-dihydroxycholecalciferol). This molecule and other naturally occurring forms of vitamin D, including its precursors and metabolites, have been modified to synthesize pharmaceuticals with potentially greater, or selective, therapeutic actions. [1] [2] [3] [4]
Vitamin D 3 (cholecalciferol) is produced industrially by exposing 7-dehydrocholesterol to UVB and UVC light, followed by purification. The 7-dehydrocholesterol is sourced as an extraction from lanolin, a waxy skin secretion in sheep's wool. [189] Vitamin D 2 (ergocalciferol) is produced in a similar way using ergosterol from yeast as a ...
Previtamin D 3 is an intermediate in the production of cholecalciferol (vitamin D 3). It is formed by the action of UV light, most specifically UVB light of wavelengths between 295 and 300 nm, acting on 7-dehydrocholesterol in the epidermal layers of the skin. [1] [2] [3] The B ring of the steroid nucleus structure is broken open, making a ...
7-Dehydrocholesterol (7-DHC) is a zoosterol that functions in the serum as a cholesterol precursor, and is photochemically converted to vitamin D 3 in the skin, therefore functioning as provitamin-D 3. The presence of this compound in human skin enables humans to manufacture vitamin D 3 (cholecalciferol).
24,25-Dihydroxycholecalciferol, also known as 24,25-dihydroxyvitamin D 3 and (24R)-hydroxycalcidiol (abbreviated as 24(R),25-(OH) 2 D 3), [1] is a compound which is closely related to 1,25-dihydroxyvitamin D 3, the active form of vitamin D 3. Like vitamin D 3 itself and calcifediol (25-hydroxyvitamin D 3), it is inactive as a hormone both in ...
Transcription of the CYP24A1 gene is markedly inducible by 1,25-(OH) 2 D 3 binding to the vitamin D receptor. [6] The gene has a strong, positive vitamin D response element in the promoter . Through regulation of CYP24A1 expression, a negative feedback control system is created to limit the effects of 1,25-(OH) 2 D 3 .