Excess 25-OH vitamin D is removed from circulation and is converted to inactive 24, 25-dihydroxy vitamin D (24,25-(OH)2-D), catalyzed by 24 hydroxylase (CYP24A1). CYP24A1 gene, encoding the vitamin ...

Given that the major vitamin D catabolizing enzyme, CYP24A1 (24-hydroxylase), is often amplified and overexpressed in tumour cells, agents that inhibit this enzyme can potentiate 1α,25(OH ...

the active form of vitamin D. 1–4,6 In addition, some of these tissues and cells express the enzyme 25-hydroxyvitamin D-1α-hydroxylase. 1–3,6 ...

Cholecalciferol, which is the side chain of vitamin D3, is then carried to the liver, where a mitochondrial hydroxylase enzyme introduces a hydroxyl group at the 25 positions. This reaction ...

25-dihydroxy vitamin D3, or 1,25-dihydroxycholecalciferol, is synthesized in the kidney in the presence of the enzyme 1α-hydroxylase. Vitamin D levels are determined by estimation of serum 25(OH ...

In this study, Dr. Patrick and Dr. Ames show that vitamin D hormone activates the gene that makes the enzyme tryptophan hydroxylase 2 (TPH2), that converts the essential amino acid tryptophan ...