Erbeznik H, Hersh L B
Department of Biochemistry, University of Kentucky, Lexington 40536-0084, USA.
Arch Biochem Biophys. 1997 Aug 1;344(1):228-34. doi: 10.1006/abbi.1997.0210.
Studies with the human lymphoma U937 cell line revealed the presence of two soluble aminopeptidase activities. Using specific antisera one of these was identified as the puromycin-specific aminopeptidase, while the other appeared to be a novel approximately 200-kDa activity. The kinetic properties of this high-molecular-weight aminopeptidase, referred to as Ap200, were similar to those of the puromycin-sensitive aminopeptidase, but showed quantitative differences. Ap200 is relatively insensitive to inhibition by both puromycin, K(i) = 27 microM, and bestatin, K(i) = 1.6 microM. Among the synthetic beta-naphthylamides, Ap200 is more specific for alanine-beta-naphthylamide compared to the puromycin-sensitive aminopeptidase. Similarly, this enzyme cleaves a more limited number of physiological peptides exhibiting a preference for the enkephalins. Ammonium sulfate, but not sodium chloride at the same ionic strength, was able to dissociate the high-molecular-weight aminopeptidase to a approximately 100-kDa active form. The high-molecular-weight aminopeptidase is found as a low abundant protein in a number of tissues including intestine, kidney, liver, lung, muscle, spleen, and testes, but could not be detected in adrenal, heart, or brain. Thus, it has a tissue distribution which differs from the puromycin-sensitive aminopeptidase.
对人淋巴瘤U937细胞系的研究揭示了两种可溶性氨肽酶活性的存在。使用特异性抗血清，其中一种被鉴定为嘌呤霉素特异性氨肽酶，而另一种似乎是一种新的约200 kDa的活性。这种高分子量氨肽酶（称为Ap200）的动力学特性与嘌呤霉素敏感氨肽酶相似，但存在定量差异。Ap200对嘌呤霉素（K(i)=27 microM）和贝抑素（K(i)=1.6 microM）的抑制相对不敏感。在合成的β-萘酰胺中，与嘌呤霉素敏感氨肽酶相比，Ap200对丙氨酸-β-萘酰胺更具特异性。同样，这种酶切割的生理肽数量更有限，对脑啡肽表现出偏好。在相同离子强度下，硫酸铵而非氯化钠能够将高分子量氨肽酶解离为约100 kDa的活性形式。高分子量氨肽酶在包括肠道、肾脏、肝脏、肺、肌肉、脾脏和睾丸在内的多种组织中以低丰度蛋白质形式存在，但在肾上腺、心脏或大脑中未检测到。因此，它的组织分布与嘌呤霉素敏感氨肽酶不同。
