Measurement of mammalian 25-hydroxyvitamin D3 24R-and 1 alpha-hydroxylase.
Measurement of mammalian 25-hydroxyvitamin D3 24R-and 1 alpha-hydroxylase.
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哺乳动物 25-羟基维生素 D3 24R-和 1 α-羟化酶的测量。
DOI：
10.1073/pnas.78.1.196
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发表时间：
1981
影响因子：
11.1
通讯作者：
DeLuca,HF
中科院分区：
文献类型：
--
作者：
Tanaka,Y;DeLuca,HF
建立了哺乳动物肾脏中25-羟基维生素D3 1 α-和24 R-羟化酶的体外测定方法。有人认为，哺乳动物血液和组织中存在的25-羟基维生素D结合蛋白通过比羟化酶更强地结合底物25-羟基维生素D3来抑制无细胞制剂中的酶活性，这种抑制作用可通过加入大量未标记的25-羟基维生素D3来饱和该蛋白的结合位点来克服。通过紫外吸收光谱法和质谱法分离并确定了大鼠肾匀浆体外产生的代谢产物为1，25-二羟基维生素D3和（24 R）-24，25-二羟基维生素D3。从维生素D缺乏大鼠制备的肾匀浆中可以证明25-羟基维生素D3的最大1 α-羟基化。这些大鼠的甲状腺甲状旁腺切除术导致1 α-羟化酶的完全抑制。给予维生素D的大鼠肾脏匀浆显示很少或没有1 α-羟化酶和大量的24 R-羟化酶活性。甲状腺甲状旁腺切除术的这些RTS显着增加24 R-羟化酶活性。
An in vitro assay of mammalian 25-hydroxyvitamin D3 1 alpha- and 24R-hydroxylases in kidney has been developed. It had been suggested that 25-hydroxyvitamin D binding protein present in mammalian blood and tissues inhibits the enzyme activities in cell-free preparations by binding the substrate 25-hydroxyvitamin D3 more strongly than the hydroxylases bind it. This inhibitory effect is overcome by the addition of substantial amounts of unlabeled 25-hydroxyvitamin D3 to saturate the binding sites of this protein. The resulting metabolites produced in vitro by rat kidney homogenates were isolated and firmly identified by ultraviolet absorption spectrometry and mass spectrometry as 1,25-dihydroxyvitamin D3 and (24R)-24,25-dihydroxyvitamin D3. Maximal 1 alpha-hydroxylation of 25-hydroxyvitamin D3 could be demonstrated in kidney homogenates prepared from vitamin D-deficient rats. Thyroparathyroidectomy of these rats resulted in total suppression of the 1 alpha-hydroxylase. Homogenates of kidney from rats given vitamin D showed little or no 1 alpha-hydroxylase and substantial 24R-hydroxylase activity. Thyroparathyroidectomy of these rts markedly increased the 24R-hydroxylase activity.