Lottaz D, Oberholzer T, Bähler P, Semenza G, Sterchi E E
Institute of Biochemistry and Molecular Biology, Faculty of Medicine, University of Berne, Switzerland.
FEBS Lett. 1992 Nov 30;313(3):270-6. doi: 10.1016/0014-5793(92)81207-3.
Maturation of human intestinal lactase-phlorizin hydrolase (LPH) requires that a precursor (pro-LPH) be proteolytically processed to the mature microvillus membrane enzyme (m-LPH). The subcellular site of this processing is unknown. Using low-temperature experiments and brefeldin A (BFA), intracellular transport was blocked in intestinal epithelial cells. In Caco-2 cells incubated at 18 degrees C, pro-LPH was complex-glycosylated but not cleaved, while at 20 degrees C small amounts of proteolytically processed LPH were observed. These data exclude a pre-Golgi proteolytic event. BFA completely blocked proteolytic maturation of LPH and lead to an aberrant form of pro-LPH in both Caco-2 cells and intestinal explants. Therefore, proteolytic processing of LPH is a post-Golgi event, occurring either in the trans-Golgi network, transport vesicles, or after insertion of pro-LPH into the microvillus membrane.
人肠乳糖酶-根皮苷水解酶（LPH）的成熟需要将前体（前LPH）进行蛋白水解加工成为成熟的微绒毛膜酶（m-LPH）。这种加工的亚细胞位点尚不清楚。通过低温实验和布雷菲德菌素A（BFA），肠道上皮细胞中的细胞内运输被阻断。在18℃孵育的Caco-2细胞中，前LPH进行了复合糖基化但未被切割，而在20℃时观察到少量经蛋白水解加工的LPH。这些数据排除了高尔基体前蛋白水解事件。BFA完全阻断了LPH的蛋白水解成熟，并在Caco-2细胞和肠道外植体中导致了异常形式的前LPH。因此，LPH的蛋白水解加工是高尔基体后事件，发生在反式高尔基体网络、运输小泡中，或者在前LPH插入微绒毛膜之后。
