A P-450 (heme-thiolate) enzyme found in the bacterium Streptomyces griseolus. cf. EC 1.14.14.24, vitamin D 25-hydroxylase and EC 1.14.15.18, calcidiol 1-monooxygenase.
wild-type, 1alpha-hydroxyvitamin D3 hydroxylation activity at C25 2.8 mmol of product per min and mol of protein, 25-hydroxyvitamin D3 hydroxylation activity at C1alpha 2.1 mmol of product per min and mol of protein
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Crystallization/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
structure of the mutant R73V/R84A with 1alpha,25-dihydroxyvitamin D3, a hydrogen-bond network including the 1alpha-hydroxyl group and several water molecules play an important role in the substrate-binding for 26-hydroxylation
wild-type to 1.5 A resolution, and mutant R84A, native protein and in complex with 1alpha,25-dihydroxyvitamin D3. The compound is positioned 11 A from the iron atom along the I helix within the pocket. The loss of two hydrogen bonds in the R84A mutant increases the adaptability of the B and F helices, creating a transient binding site
1alpha-hydroxyvitamin D3 hydroxylation activity at C25 5.4 mmol of product per min and mol of protein, 25-hydroxyvitamin D3 hydroxylation activity at C1alpha 3.4 mmol of product per min and mol of protein
1alpha-hydroxyvitamin D3 hydroxylation activity at C25 0.48 mmol of product per min and mol of protein, 25-hydroxyvitamin D3 hydroxylation activity at C1alpha 0.72 mmol of product per min and mol of protein
1alpha-hydroxyvitamin D3 hydroxylation activity at C25 0.33 mmol of product per min and mol of protein, 25-hydroxyvitamin D3 hydroxylation activity at C1alpha 0.31 mmol of product per min and mol of protein
1alpha-hydroxyvitamin D3 hydroxylation activity at C25 30.9 mmol of product per min and mol of protein, 25-hydroxyvitamin D3 hydroxylation activity at C1alpha 20.8 mmol of product per min and mol of protein
variant is also capable of converting vitamin D2 to its active form, that is, 1alpha,25-dihydroxyvitamin D2, via 25-hydroxyvitamin D2, with its 1alpha-hydroxylation activity toward 25-hydroxyvitamin D2 being much lower than that toward 25-hydroxyvitamin D3. The substitutions enhance both 25- and 26-hydroxylation activity toward vitamin D2. After 25-hydroxylation of vitamin D2, further hydroxylation at C26 may occur frequently without the release of 25-hydroxyvitamin D2 from the substrate-binding pocket
1alpha-hydroxyvitamin D3 hydroxylation activity at C25 75.7 mmol of product per min and mol of protein, 25-hydroxyvitamin D3 hydroxylation activity at C1alpha 34.5 mmol of product per min and mol of protein
mutation gives preference to the 1alpha-hydroxylation of 25-hydroxyvitamin D 3 over the 25-hydroxylation of 1alpha-hydroxyvitamin D 3, opposite to the wild type
1alpha-hydroxyvitamin D3 hydroxylation activity at C25 0.25 mmol of product per min and mol of protein, no 25-hydroxyvitamin D3 hydroxylation activity at C1alpha
1alpha-hydroxyvitamin D3 hydroxylation activity at C25 4.6 mmol of product per min and mol of protein, 25-hydroxyvitamin D3 hydroxylation activity at C1alpha 3.4 mmol of product per min and mol of protein
1alpha-hydroxyvitamin D3 hydroxylation activity at C25 1.52 mmol of product per min and mol of protein, 25-hydroxyvitamin D3 hydroxylation activity at C1alpha 0.34 mmol of product per min and mol of protein
variant is also capable of converting vitamin D2 to its active form, that is, 1alpha,25-dihydroxyvitamin D2, via 25-hydroxyvitamin D2, with its 1alpha-hydroxylation activity toward 25-hydroxyvitamin D2 being much lower than that toward 25-hydroxyvitamin D3. The substitutions enhance both 25- and 26-hydroxylation activity toward vitamin D2. After 25-hydroxylation of vitamin D2, further hydroxylation at C26 may occur frequently without the release of 25-hydroxyvitamin D2 from the substrate-binding pocket
mutant exhibits 435- and 110fold higher kcat/Km values for the 25-hydroxylation of 1alpha-hydroxyvitamin D3 and 1alpha-hydroxylation of 25-hydroxyvitamin D3, respectively, compared with the wild-type
expression of mutant R73V/R84A in Streptomyces lividans TK23 cells under the control of the tipA promoter leads to synthesis of 25-hydroxyvitamin D3 and large amounts of 1alpha,25-dihydroxyvitamin D3. In addition, polar metabolites 1alpha,25(R),26-trihydroxyvitamin D3 and 1alpha,25(R),26-trihydroxyvitamin D3 are observed at a ratio of 5:1