Mammalian intestinal alkaline phosphatase acts as highly active exopolyphosphatase
Mammalian intestinal alkaline phosphatase acts as highly active exopolyphosphatase
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DOI：
10.1016/s0167-4838(01)00193-5
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发表时间：
2001-06-11
期刊：
影响因子：
--
通讯作者：
Schröder, HC
中科院分区：
文献类型：
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作者：
Lorenz, B;Schröder, HC
最近的研究结果表明，无机多磷酸盐（polyP），是一种富含能量的线性聚合物的正磷酸盐残基已知的细菌和酵母，也存在于高等真核生物。然而，其代谢的酶基础，特别是在哺乳动物细胞中仍然不确定。在这里，我们首次证明了来自小牛肠的碱性磷酸酶（CIAP）能够切割链长约800的polyP分子，该酶作为外聚磷酸酶以进行性方式降解polyP。最佳pH值在碱性范围内。二价阳离子对于催化活性不是必需的，但抑制聚P的降解。CIAP对短链聚P的水解速率与标准碱性磷酸酶（AP）底物磷酸对硝基苯基酯的水解速率相当。在碱性和中性pH范围内，酶的比活性随着聚合物链长的增加而降低。随着链长的增加，酶的Ki也降低。AP的哺乳动物组织非特异性同种型在所施加的条件下不能水解聚P，而胎盘型AP和细菌（大肠杆菌）AP显示聚P降解活性。(C)出版社：Elsevier Science B.V.
Recent results revealed that inorganic polyphosphates (polyP), being energy-rich linear polymers of orthophosphate residues known from bacteria and yeast, also exist in higher eukaryotes. However, the enzymatic basis of their metabolism especially in mammalian cells is still uncertain. Here we demonstrate for the first time that alkaline phosphatase from calf intestine (CIAP) is able to cleave polyP molecules up to a chain length of about 800, The enzyme acts as an exopolyphosphatase degrading polyP in a processive manner. The pH optimum is in the alkaline range. Divalent cations are not required for catalytic activity but inhibit the degradation of polyP. The rate of hydrolysis of short-chain polyP by CIAP is comparable to that of the standard alkaline phosphatase (AP) substrate p-nitrophenyl phosphate. The specific activity of the enzyme decreases with increasing chain length of the polymer both in the alkaline and in the neutral pH range. The K, of the enzyme also decreases with increasing chain length. The mammalian tissue non-specific isoform of AP was not able to hydrolyze polyP under the conditions applied while the placental-type AP and the bacterial (Escherichia coli) AP displayed polyP-degrading activity. (C) 2001 Published by Elsevier Science B.V.