1-alpha,24,26-trihydroxy-vitamin D2, 1.14.13.- 1.14.14.-, 25-OH- vitamin D2, 1.14.-.-, 24-OH- vitamin D2, Vitamin D2, 1alpha-,24-dihydroxy-26-carboxy-vitamin D2, 1.14.-.-, 1.14.-.-, 1,25-Dihydroxyvitamin D2, 1.14.-.-, CYP3A4, 1alfa-,25-,26-trihydroxy-24-oxo-vitamin D2, 1.14.-.-, CYP27A1, 24-OH- vitamin D2, 1.14.-.-, CYP2R1, 1.14.-.-, 1.14.-.-, 1,24-Dihydroxyvitamin D2, 24,25-Dihydroxyvitamin D2, 1.14.-.-, 1-alfa-,24(R)-,25-,26-Tetrahydroxy-Vitamin D2, 1.14.-.-, 1alpha-,23-,25-,26-tetrahydroxy-24-oxo-vitamin D2, 1-alfa-,24-,25-,28-(OH)4-vitamin D2, 1,25-Dihydroxyvitamin D2, CYP2C9, 1.14.-.-, 1.14.13.- 1.14.14.-, 25-OH- vitamin D2, 1,24-Dihydroxyvitamin D2, 1.14.-.-, CYP27B1, Calcitroic acid, 1-alfa-,24-,25-(OH)3-vitamin D2, CYP24A1, 1.14.-.-, 1,23-Dihydroxy-24,25,26,27- tetranorvitamin D3, Doxercalciferol, 1.14.-.-
Vitamin D2 (ergocalciferol) metabolism
The first step of Vitamin D2 metabolism is a side-chain hydroxylation in the liver carried out by specific cytochrome P450 enzymes. The hydroxylation reactions can be catalyzed by Cytochrome P450, family 3, subfamily A, polypeptide 4 ( CYP3A4 ) ,  and Cytochrome P450, family 27, subfamily A, polypeptide 1 ( CYP27A1 ) , , , ,  and result in formation of 24-OH-vitamin D2 metabolite. Alternatively the reactions can be catalyzed by CYP27A1 , CYP3A4 , , Cytochrome P450, family 2, subfamily C, polypeptide 9 ( CYP2C9 )  and cytochrome Cytochrome P450, family 2, subfamily R, polypeptide 1 ( CYP2R1 ) , ,  to produce 25-OH-vitamin D2 metabolite.
Vitamin D2 analogue Doxercalciferol is also hydroxylated by CYP27A1 and CYP3A4 to form 1,24-Dihydroxyvitamin D2 , , ,  and 1,25-Dihydroxyvitamin D2 ,  as products. The latter metabolites are also formed during the subsequent metabolic steps in kidney. In particular, 1,24-Dihydroxyvitamin D2 and 1,25-Dihydroxyvitamin D2 are products of hydroxylation of, respectively, 24-OH-vitamin D2 and 25-OH-vitamin D2 catalyzed by Cytochrome P450, family 27, subfamily B, polypeptide 1 ( CYP27B1 ) , , .
1,24-Dihydroxyvitamin D2 is further hydroxylated by CYP27A1 and cytochrome Cytochrome P450, family 24, subfamily A, polypeptide 1 ( CYP24A1 ) to form a 1-alpha,24,26-trihydroxy-vitamin D2 trihydroxylated metabolite ,  that undergoes subsequent oxidation at C-26 catalyzed by CYP24A1 ,  with 1alpha-,24-dihydroxy-26-carboxy-vitamin D2 as a product.
25-OH-vitamin D2 can be further hydroxylated by CYP24A1 when a 24,25-Dihydroxyvitamin D2 metabolite is formed .
The same P450 enzyme catalyzes all further steps of 1,25-Dihydroxyvitamin D2 degradation that include: hydroxylation at C-24 to form 1-alfa-,24-,25-(OH)3-vitamin D2 as a product and subsequent hydroxylation at C-28 to form 1-alfa-,24-,25-,28-(OH)4-vitamin D2. The following hydroxyl group migration results in production of stereo isomers of which only 1-alfa-,24(R)-,25-,26-Tetrahydroxy-Vitamin D2 participates in C-24 hydroxyl group oxidation to form 1alfa-,25-,26-trihydroxy-24-oxo-vitamin D2 metabolite. This metabolite is then hydroxylated to 1alpha-,23-,25-,26-tetrahydroxy-24-oxo-vitamin D2 and undergoes a side-chain degradation to 1,23-Dihydroxy-24,25,26,27-tetranorvitamin D3. At the final stage, the latter metabolite is oxidized to form Calcitroic acid.