Bauvois B
Laboratoire de Physiopathologie du Développement, CNRS URA 230, Paris, France.
Eur J Immunol. 1990 Mar;20(3):459-68. doi: 10.1002/eji.1830200302.
Murine thymocytes are shown to possess at least three well-defined exo-N-aminopeptidase activities on their surface. One of them cleaves the prolyl bond in the synthetic dipeptide nitroanilide Gly-Pro-pNA (Km 0.95 mM and Vmax 8 nmol/h at pH 7.4 and 37 degrees C) and is specifically inhibited by phenylmethane sulfonyl fluoride, diprotin A, Gly-Pro-Ala and Gly-Pro-Gly-Gly. These data further support identification of this enzyme with a serine exopeptidase dipeptidyl peptidase IV (DPP IV), previously reported to be specific for collagen. The two other forms of N-exopeptidase activities are detected when Ala-pNA and Leu-pNA are used as substrates. Leu-aminopeptidase activity (Km 1.4 mM, Vmax 15 nmol/h) and Ala-aminopeptidase activity (Km 4.0 mM, Vmax 20 nmol/h) are inhibited by inhibitors for thiol- and trypsin-like proteinases, i.e. tosyl lysyl chloromethyl ketone, leupeptin and N-ethylmaleimide. Addition inhibition of Leu-aminopeptidase activity by peptstatin, a known inhibitor of carboxyl proteases, suggests that aminopeptidase activity detected with Leu-pNA is different in part from Ala-aminopeptidase activity. Among the various lymphoid cell populations tested, the three aminopeptidase activities are increased by three- to fourfold in the immature CD4-CD8- thymocyte subset as well as in the thymoma BW5147. In contrast, cortisone-resistant thymocytes, lymph node and spleen cells exhibit levels of activities almost similar to that of unfractionated thymocytes. During ontogeny, the levels of these activities are increased four- to sevenfold on fetal thymocytes (from days 14 to 16). Finally, when thymocytes or spleen cells are cultured with a mitogenic concentration of concanavalin A, their proliferative responses are correlated with an enhancement of the aminopeptidase activities (1.3- to 5-fold). From these results, a correlation between the presence of these peptidases on the cell surface of immature and mature lymphoid cells and biological responsiveness is suggested.
已表明小鼠胸腺细胞表面至少具有三种明确的外切N - 氨肽酶活性。其中一种能切割合成二肽硝基苯胺Gly - Pro - pNA中的脯氨酰键（在pH 7.4和37℃时，Km为0.95 mM，Vmax为8 nmol/h），并被苯甲基磺酰氟、二丙基丁二胺、Gly - Pro - Ala和Gly - Pro - Gly - Gly特异性抑制。这些数据进一步支持将该酶鉴定为丝氨酸外肽酶二肽基肽酶IV（DPP IV），此前报道该酶对胶原蛋白具有特异性。当使用Ala - pNA和Leu - pNA作为底物时，可检测到另外两种形式的N - 外肽酶活性。亮氨酰氨肽酶活性（Km为1.4 mM，Vmax为15 nmol/h）和丙氨酰氨肽酶活性（Km为4.0 mM，Vmax为20 nmol/h）被巯基和类胰蛋白酶样蛋白酶的抑制剂抑制，即甲苯磺酰赖氨酰氯甲基酮、亮抑酶肽和N - 乙基马来酰亚胺。羧基蛋白酶的已知抑制剂胃酶抑素对亮氨酰氨肽酶活性的额外抑制表明，用Leu - pNA检测到的氨肽酶活性部分不同于丙氨酰氨肽酶活性。在测试的各种淋巴细胞群体中，未成熟的CD4 - CD8 - 胸腺细胞亚群以及胸腺瘤BW5147中的三种氨肽酶活性增加了三到四倍。相比之下，耐可的松的胸腺细胞、淋巴结和脾细胞的活性水平与未分级的胸腺细胞几乎相似。在个体发育过程中，这些活性水平在胎儿胸腺细胞（第14至16天）上增加了四到七倍。最后，当胸腺细胞或脾细胞用促有丝分裂浓度的伴刀豆球蛋白A培养时，它们的增殖反应与氨肽酶活性的增强相关（1.3至5倍）。从这些结果表明，未成熟和成熟淋巴细胞细胞表面这些肽酶的存在与生物学反应性之间存在相关性。
