Imaizumi T, Jyonouchi K, Kato T, Chikuma T, Tanaka A
Department of Pharmaceutical Analytical Chemistry, Showa College of Pharmaceutical Sciences, Machida-shi, 3-3165 Higashi-tamagawagakuen, Tokyo, Japan.
Biochim Biophys Acta. 2000 Feb 9;1476(2):337-49. doi: 10.1016/s0167-4838(99)00239-3.
Axonal transport of Boc-Arg-Val-Arg-Arg-MCA hydrolyzing enzyme activity was studied in rat sciatic nerves from 12 to 120 h after double ligations. The anterograde axonal transport increased and peaked 72 h after ligation. The optimum pH for Boc-Arg-Val-Arg-Arg-MCA hydrolyzing enzyme activity was 6.5 to 6.9 and did not require Ca(2+) for the activity. Two molecular forms with enzyme activity were identified by size-exclusion chromatography and the molecular masses of the two enzymes were estimated to be 98 and 52 kDa. Two enzyme activities were strongly inhibited by Hg(2+), Cu(2+) and trypsin inhibitors such as TLCK, antipain and leupeptin. It cleaved the substrate, Boc-Arg-Val-Arg-Arg-MCA, between the dibasic sequence Arg-Arg, and needed a support of aminopeptidase B-like enzyme activity for the liberation of 7-amino-4-methylcoumarin. These results suggest that the enzyme is transported in rat sciatic nerves and involved in the post-translational processing of precursor proteins under the anterograde axonal transport. But there is absolutely no evidence for a role in precursor processing and such a putative role is purely speculative.
在双结扎后12至120小时，对大鼠坐骨神经中Boc-Arg-Val-Arg-Arg-MCA水解酶活性的轴突运输进行了研究。顺行性轴突运输在结扎后72小时增加并达到峰值。Boc-Arg-Val-Arg-Arg-MCA水解酶活性的最适pH为6.5至6.9，且该活性不需要Ca(2+)。通过尺寸排阻色谱法鉴定出两种具有酶活性的分子形式，两种酶的分子量估计分别为98 kDa和52 kDa。两种酶活性均受到Hg(2+)、Cu(2+)以及胰蛋白酶抑制剂（如TLCK、抗痛素和亮抑酶肽）的强烈抑制。它在二肽序列Arg-Arg之间切割底物Boc-Arg-Val-Arg-Arg-MCA，并且需要氨肽酶B样酶活性的支持才能释放7-氨基-4-甲基香豆素。这些结果表明，该酶在大鼠坐骨神经中运输，并在顺行性轴突运输下参与前体蛋白的翻译后加工。但绝对没有证据表明其在前体加工中起作用，这种假定的作用纯粹是推测性的。
