Lendeckel U, Wex T, Kähne T, Frank K, Reinhold D, Ansorge S
Department of Internal Medicine, University of Magdeburg, Germany.
Cell Immunol. 1994 Jan;153(1):214-26. doi: 10.1006/cimm.1994.1019.
The membrane-bound metalloprotease aminopeptidase N (APN, CD13, EC 3.4.11.2) is a well-established marker of normal and malignant cells of the myelomonocytic lineages. It is also expressed by leukemic blasts of a small group of patients suffering from acute or chronic lymphoid leukemia. CD13-specific monoclonal antibodies do not bind to the surface of normal B lymphocytes and APN-mRNA was not detectable by Northern analysis in normal lymphocytes or in T cell lines. A recent paper, however, describes the expression of CD13 on concanavalin A-stimulated T cells. Here, by means of enzymatic amplification of cDNA, cloning and sequencing of amplified cDNA fragments, in situ hybridization, and transcription start site mapping, evidence is provided that the human T cell lines HuT78 and H9 do contain APN-mRNA. Ala-pNA-hydrolyzing activity was detected in viable cells and cell homogenates as well as in size-fractionated protein fractions. Alanine-beta-naphthylamide (Ala-beta NA)-hydrolyzing activity was readily detectable after isoelectric focusing and blotting and was shown to be localized exclusively intracellularly in both cell lines. Usage of aminopeptidase-specific effectors revealed this activity to be distinct from CD13.
膜结合金属蛋白酶氨肽酶N（APN，CD13，EC 3.4.11.2）是髓单核细胞系正常细胞和恶性细胞的一种公认标志物。一小部分急性或慢性淋巴细胞白血病患者的白血病原始细胞也表达该标志物。CD13特异性单克隆抗体不与正常B淋巴细胞表面结合，并且通过Northern分析在正常淋巴细胞或T细胞系中检测不到APN - mRNA。然而，最近一篇论文描述了CD13在伴刀豆球蛋白A刺激的T细胞上的表达。在此，通过cDNA的酶促扩增、扩增的cDNA片段的克隆和测序、原位杂交以及转录起始位点定位，提供了证据表明人T细胞系HuT78和H9确实含有APN - mRNA。在活细胞、细胞匀浆以及大小分级的蛋白质组分中检测到了水解Ala - pNA的活性。在等电聚焦和印迹后很容易检测到水解丙氨酸 - β - 萘酰胺（Ala - βNA）的活性，并且显示该活性仅定位于两种细胞系的细胞内。使用氨肽酶特异性效应物表明该活性与CD13不同。
