Shimamura M, Hazato T, Iwaguchi T
Department of Cancer Therapeutics, Tokyo Metropolitan Institute of Medical Science, Japan.
Brain Res. 1988 Apr 5;445(2):350-3. doi: 10.1016/0006-8993(88)91197-3.
A new aminopeptidase, which cleaves the Tyr1-Gly2 bond of enkephalin, was partially purified from the monkey brain membrane fraction. The molecular weight of the enzyme was estimated to be about 53,000, and the optimum pH was in the neutral region (pH 6.5). The enzyme hydrolyzed Leu-enkephalin with a Km value of 238 microM. It strongly hydrolyzed L-tyrosine and L-leucine beta-naphthylamide, but showed only weak affinity for L-arginine or L-alanine beta-naphthylamide. The enzyme was much more potently inhibited by bestatin (IC50: 2 x 10(-8) M) than the other specific aminopeptidase inhibitors examined, while it showed low sensitivity to puromycin and actinonin, inhibitors of cerebral enkephalin-degrading aminopeptidase and aminopeptidase M, respectively. These results indicate that the new enkephalin-degrading aminopeptidase is clearly distinct from aminopeptidase M, which has been reported to be a key enzyme in enkephalin inactivation.
从猴脑膜组分中部分纯化出一种新的氨肽酶，它能裂解脑啡肽的Tyr1-Gly2键。该酶的分子量估计约为53,000，最适pH在中性范围（pH 6.5）。该酶水解亮氨酸脑啡肽的Km值为238 microM。它能强烈水解L-酪氨酸和L-亮氨酸β-萘酰胺，但对L-精氨酸或L-丙氨酸β-萘酰胺的亲和力较弱。与所检测的其他特异性氨肽酶抑制剂相比，该酶受苯丁抑制素（IC50：2×10(-8) M）的抑制作用更强，而它对嘌呤霉素和放线菌素的敏感性较低，这两种物质分别是脑内脑啡肽降解氨肽酶和氨肽酶M的抑制剂。这些结果表明，这种新的脑啡肽降解氨肽酶与氨肽酶M明显不同，据报道氨肽酶M是脑啡肽失活的关键酶。
