Miltyk W, Karna E, Wołczyński S, Pałka J
Department of Medicinal Chemistry, Medical Academy of Białystok, Poland.
Mol Cell Biochem. 1998 Dec;189(1-2):177-83. doi: 10.1023/a:1006958116586.
Prolidase [E.C.3.4.13.9] is a cytosolic exopeptidase that catalyses the hydrolysis of C-terminal proline containing dipeptides or tripeptides. The enzyme plays an important role in the recycling of proline for collagen synthesis. Increase in enzyme activity is correlated with increased rates of collagen turnover but the mechanism and endpoints by which this enzyme is regulated remain largely unknown. We have found that insulin-like growth factor-I (IGF-I), potent stimulator of collagen biosynthesis, induces prolidase activity in cultured human skin fibroblasts. Supporting evidence comes from the following observations: (1) Serum of fasted rats, (IGF-I, 72 +/- 16 ng/ml) showed about 50% reduced ability to stimulate prolidase activity and collagen biosynthesis in confluent fibroblasts in comparison to the effect of control rat serum (IGF-I, 168 +/- 29). (2) An addition of IGF-I (100 ng/ml) to fasted rat serum restored its ability to stimulate prolidase activity and collagen biosynthesis to control values. (3) In confluent human skin fibroblasts, cultured for 48 h with serum free medium prolidase activity was decreased to 50% of control cells, cultured in the presence of normal rat serum. Supplementation of serum free medium with EGF, PDGF and IGF-I (factors that can replace growth promoting activity of serum) stimulated prolidase activity to control values while the medium deprived IGF-I had no such effect. (4) The relative differences in prolidase activity due to specific treatment of confluent cells with above growth factors were accompanied by parallel differences in the amount of the enzyme protein recovered from these cells as shown by western immunoblot analysis. Thus we conclude that prolidase activity is regulated by IGF-I in confluent fibroblasts.
脯氨酰二肽酶[E.C.3.4.13.9]是一种胞质外肽酶，可催化含C末端脯氨酸的二肽或三肽的水解。该酶在脯氨酸循环用于胶原蛋白合成中起重要作用。酶活性的增加与胶原蛋白周转速率的增加相关，但该酶的调节机制和终点仍 largely unknown。我们发现胰岛素样生长因子-I（IGF-I），一种胶原蛋白生物合成的有效刺激剂，可诱导培养的人皮肤成纤维细胞中的脯氨酰二肽酶活性。支持证据来自以下观察结果：（1）与对照大鼠血清（IGF-I，168±29）的作用相比，禁食大鼠的血清（IGF-I，72±16 ng/ml）刺激汇合的成纤维细胞中脯氨酰二肽酶活性和胶原蛋白生物合成的能力降低约50%。（2）向禁食大鼠血清中添加IGF-I（100 ng/ml）可将其刺激脯氨酰二肽酶活性和胶原蛋白生物合成的能力恢复到对照值。（3）在无血清培养基中培养48小时的汇合人皮肤成纤维细胞中，脯氨酰二肽酶活性降至在正常大鼠血清存在下培养的对照细胞的50%。用表皮生长因子（EGF）、血小板衍生生长因子（PDGF）和IGF-I（可替代血清生长促进活性的因子）补充无血清培养基可将脯氨酰二肽酶活性刺激至对照值，而缺乏IGF-I的培养基则无此作用。（4）如蛋白质免疫印迹分析所示，汇合细胞用上述生长因子进行特异性处理后，脯氨酰二肽酶活性的相对差异伴随着从这些细胞中回收的酶蛋白量的平行差异。因此，我们得出结论，在汇合的成纤维细胞中，脯氨酰二肽酶活性受IGF-I调节。
