Indentification of an intestinal sodium and calcium-dependent phosphatase stimulated by parathyroid hormone.
Indentification of an intestinal sodium and calcium-dependent phosphatase stimulated by parathyroid hormone.
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甲状旁腺激素刺激的肠道钠和钙依赖性磷酸酶的鉴定。
DOI：
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发表时间：
1974
影响因子：
15.9
通讯作者：
H. Gilbert
中科院分区：
文献类型：
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作者：
S. Birge;H. Gilbert
先前的报告表明，能量依赖性肠钙转运对抗电势和浓度梯度的位点位于粘膜细胞的基底外侧膜上。因此，从大鼠肠匀浆中制备基底侧膜，以鉴定介导转运过程中这一步骤的酶。描述了一种碱性磷酸酶，它利用 ATP 作为底物，依赖于 Na(-) 和 Ca(++)，最佳酶活性分别为 200 mM 和 0.04 mM。此外，该酶的活性被证明随着动物年龄的增长而降低，并且随着甲状旁腺的去除而降低，这与在相同实验条件下粘膜细胞释放(45)Ca的速率降低一致。钙与基底侧膜碎片的结合也是钠依赖性的，并且通过预先施用甲状旁腺提取物而增强。在各种实验条件下，跨粘膜细胞基底外侧膜的钙转运速率与这种 Na、Ca 依赖性磷酸酶的活性之间一致的相关性表明，该酶可能介导甲状旁腺激素敏感的钙跨肠道主动转运。
Previous reports suggest that the site of the energy-dependent intestinal calcium transport against an electropotential and concentration gradient is located along the basal-lateral membrane of the mucosal cell. Accordingly, basal-lateral membranes were prepared from rat intestinal homogenates in order to identify the enzyme mediating this step in the transport process. An alkaline phosphatase was delineated which utilized ATP as a substrate and was dependent on both Na(-) and Ca(++) with optimum enzyme activity at 200 mM and 0.04 mM, respectively. Furthermore, the activity of the enzyme was demonstrated to decrease with the advance in age of the animal and to decrease with removal of the parathyroid glands, consistent with a decreased rate of (45)Ca release from mucosal cells under the same experimental conditions. Calcium binding to basal-lateral membrane fragments was also sodium dependent and enhanced by the prior administration of parathyroid extract. The consistent correlation between the rate of calcium transport across the basal-lateral membrane of the mucosal cell and the activity of this Na, Ca-dependent phosphatase under a variety of experimental conditions suggest that this enzyme may mediate the parathyroid hormone-sensitive active transport of calcium across the intestine.