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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. [184] Vitamin D 2 (ergocalciferol) is produced in a similar way using ergosterol from yeast as a ...
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 .
The basic unit of the Reactome database is a reaction; reactions are then grouped into causal chains to form pathways [115] The Reactome data model allows us to represent many diverse processes in the human system, including the pathways of intermediary metabolism, regulatory pathways, and signal transduction, and high-level processes, such as ...
CYP2R1 is cytochrome P450 2R1, an enzyme which is the principal vitamin D 25-hydroxylase. [5] [6] In humans it is encoded by the CYP2R1 gene located on chromosome 11p15.2. [7]It is expressed in the endoplasmic reticulum in liver, where it performs the first step in the activation of vitamin D by catalyzing the formation of 25-hydroxyvitamin D. [8]
The vitamin D receptor (VDR also known as the calcitriol receptor) is a member of the nuclear receptor family of transcription factors. [5] Calcitriol (the active form of vitamin D , 1,25-(OH) 2 vitamin D 3 ) binds to VDR, which then forms a heterodimer with the retinoid-X receptor .
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).
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Calcifediol binds in the blood to vitamin D-binding protein (also known as gc-globulin) and is the main circulating vitamin D metabolite. [4] [5] Calcifediol has an elimination half-life of around 15 to 30 days. [4] [9] Calcifediol is further hydroxylated at the 1-alpha-position in the kidneys to form 1,25-(OH) 2 D 3, calcitriol.