CYP24A1 hydroxylates 1,25(OH)2D, inactivating it

Stable Identifier
Reaction [transition]
Homo sapiens
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1-alpha, 25-dihydroxyvitamin D (1,25(OH)2D) is biologically inactivated through a series of reactions beginning with 24-hydroxylation and is most likely a mechanism of elimination. 24-Hydroxylation of vitamin D metabolites is largely regulated inversely to 1-hydroxylation, the initial step towards activation. Human cDNA encoding CYP24A1 was isolated in 1993 (Chen et al. 1993). Studies with expressed human CYP24A1 in Sf21 insect cells indicated that the enzyme could catalyze most, if not all, of the steps in the C23 and C24 oxidation pathways of 25(OH)D and 1,25(OH)2D metabolism (Beckman et al. 1996). Sakaki et al observed that the ratio of initial hydroxylation products at C24 to C23 was 4:1, indicating that the C24-oxidation pathway predominates in humans (Sakaki et al. 2000).
Literature References
PubMed ID Title Journal Year
8679605 Human 25-hydroxyvitamin D3-24-hydroxylase, a multicatalytic enzyme

Beckman, MJ, DeLuca, HF, Yamada, S, Prahl, J, Tadikonda, P, Werner, E

Biochemistry 1996
8506296 Isolation and expression of human 1,25-dihydroxyvitamin D3 24-hydroxylase cDNA

Prahl, JM, Chen, KS, DeLuca, HF

Proc Natl Acad Sci U S A 1993
11012668 Dual metabolic pathway of 25-hydroxyvitamin D3 catalyzed by human CYP24

Komai, K, Sawada, N, Ohyama, Y, Shiozawa, S, Sakaki, T, Yamada, S, Inouye, K, Yamamoto, K

Eur J Biochem 2000
Catalyst Activity

1-alpha,25-dihydroxyvitamin D3 24-hydroxylase activity of CYP24A1 [mitochondrial inner membrane]

This event is regulated
Positively by
Orthologous Events
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