FIGURE 7-1 The photochemical, thermal, and metabolic pathways for vitamin D3. Specific enzymes abbreviated as follows: ∆7ase,7-dehydrocholesterol reductase; 25OHase, vitamin D-25-hydroxylase; 1α-OHase, 25-OH-D-1α-hydroxylase; 24R-OHase, 25(OH)D-24R-hydroxylase. Inset: the structure of vitamin D2. Reproduced with permission, Holick (1996).
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