Properties of a calcium-activated protease in squid axoplasm which selectively degrades neurofilament proteins.
Properties of a calcium-activated protease in squid axoplasm which selectively degrades neurofilament proteins.
复制标题
鱿鱼轴浆中钙激活蛋白酶的特性，可选择性降解神经丝蛋白。
DOI：
10.1002/neu.480110102
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发表时间：
1980
期刊：
影响因子：
--
通讯作者：
Harold Gainer
中科院分区：
文献类型：
--
作者：
H. Pant;H. Pant;Harold Gainer;Harold Gainer
从鱿鱼的巨大轴突中挤出的轴浆含有Ca2+激活的蛋白酶。 100,000 x g 轴浆上清液中的蛋白酶非常特异，仅降解 200,000 MW 的神经丝蛋白 (NF200)，而沉淀中的蛋白酶具有更广泛的底物特异性。上清液蛋白酶的激活仅限于Ca2+离子，没有其他二价阳离子可以替代。该蛋白酶需要高于 0.5 mM 浓度的 Ca2+ 才能激活，最适 pH 值约为 7.5。 NF200 的降解似乎经历了 100,000 MW，并可能经历 47,000--50,000 MW 中间形式，然后降解为 TCA 可溶性肽。蛋白酶的活性受到二价阳离子螯合剂、Cu2+ 和 Fe2+、巯基抑制剂和亮肽素的抑制。鱿鱼轴浆中的这种特定的 Ca2+ 激活蛋白酶与各种非神经组织中发现的 Ca2+ 激活蛋白酶具有相同的特性。尽管其蛋白质底物特异性较窄，但从人血小板中纯化的 Ca2+ 激活蛋白酶可有效降解鱿鱼 NF200，这表明血小板和肌肉肌动蛋白结合蛋白以及神经丝蛋白之间可能存在结构关系。
Axoplasm extruded from the giant axon of the squid contains Ca2+-activated proteases. The protease in the 100,000 x g of supernatant of axoplasm is very specific and degrades only the 200,000 MW, neurofilament protein (NF200), whereas the protease(s) in the pellet has a much wider range of substrate specificity. The activation of the supernatant protease is restricted to the Ca2+ ion, and no other divalent cation will substitute. The protease requires Ca2+ at a higher concentration than 0.5 mM for activation, and has a pH optimum of about 7.5. Degradation of the NF200 appears to proceed through a 100,000 MW and possibly a 47,000--50,000-MW intermediate form before degradation to TCA-soluble peptides. Activity of the protease is inhibited by divalent cation chelators, Cu2+ and Fe2+, sulphydryl inhibitors, and leupeptin. This specific Ca2+-activated protease in squid axoplasm has identical properties to Ca2+-activated proteases found in various non-neural tissues. Despite its narrow protein substrate specificity, Ca2+-activated protease purified from human platelets effectively degrades squid NF200, suggesting a possible structural relationship between platelet and muscle actin-binding proteins and neurofilament proteins.