Ads
related to: vitamin d pathway in body parts worksheet for grade 1
Search results
Results From The WOW.Com Content Network
A third important effect of PTH on the kidneys is stimulation of the conversion of 25-hydroxy vitamin D into 1,25-dihydroxy vitamin D (calcitriol). [210] This form of vitamin D is the active hormone which promotes calcium uptake from the intestine via the action of calbindin. [212] Calcitriol also reduces calcium loss to urine. [209]
25-Hydroxyvitamin D 1-alpha-hydroxylase (VD 1A hydroxylase) also known as calcidiol 1-monooxygenase [5] or cytochrome p450 27B1 (CYP27B1) or simply 1-alpha-hydroxylase is a cytochrome P450 enzyme that in humans is encoded by the CYP27B1 gene. [6] [7] [8]
These two forms of vitamin D are metabolized in the liver and stored as 25-hydroxyvitamin D. [4] Before biological use, the storage form must be converted into an active form. One common active form is 1,25-dihydroxyvitamin D. [4] The term vitamin D in this article means cholecalciferol, ergocalciferol, 25-hydroxyvitamin D, and the active forms ...
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]
CYP24A1 also is able to catalyze another pathway which starts with 23-hydroxylation of 1,25-(OH) 2 D 3 and culminates in 1,25-(OH) 2 D 3-26,23-lactone. [ 6 ] The side chains of the ergocalciferol (vitamin D 2 ) derivatives, 25-OH-D 2 and 1,25-(OH) 2 D 2 , are also hydroxylated by CYP24A1.
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).