Department of Medical Biochemistry, University of Gothenburg, P.O. Box 440, 40530 Gothenburg, Sweden.
Benef Microbes. 2010 Nov;1(4):343-50. doi: 10.3920/BM2010.0039.
The colon epithelium is covered by two layers of mucus built around the MUC2 mucin. An inner dense and attached mucus layer does not allow bacteria to penetrate, thus keeping the epithelial cell surface free from bacteria. An outer loose mucus layer is the habitat for the commensal bacterial microbiota. The inner mucus layer is renewed from the epithelial side and gets converted into the outer layer due to proteolytic cleavages by host proteases. We have now analysed if potential probiotic bacteria, namely Lactobacillus brevis, Lactobacillus plantarum, Lactobacillus bulgaricus and Bifidobacterium lactis, can secrete protease that cleaves the MUC2 mucin. We found that none of the potential probiotic bacteria Lactobacillus and Bifidobacterium could cleave the MUC2 core protein in the form of recombinant MUC2 N and C-termini although they secreted active proteases. This was in contrast to crude mixtures of oral and faecal bacteria that cleaved the MUC2 mucin. This observation further supports the view that these potential probiotic bacteria are of no harm to the host, as these bacteria cannot disrupt the mucin organised mucus as long as they are covered by glycans.
结肠上皮由两层围绕 MUC2 粘蛋白形成的粘液覆盖。内层致密且附着的粘液层不允许细菌穿透，从而使上皮细胞表面免受细菌侵害。外层疏松的粘液层是共生菌菌群的栖息地。内层粘液层从上皮侧更新，并由于宿主蛋白酶的蛋白水解裂解而转化为外层。我们现在分析了潜在的益生菌细菌，即短乳杆菌、植物乳杆菌、保加利亚乳杆菌和乳双歧杆菌，是否能分泌蛋白酶裂解 MUC2 粘蛋白。我们发现，尽管潜在的益生菌细菌乳酸菌和双歧杆菌分泌有活性的蛋白酶，但它们不能裂解以重组 MUC2 N 和 C 末端形式存在的 MUC2 核心蛋白。这与口腔和粪便细菌的粗混合物能裂解 MUC2 粘蛋白形成对比。这一观察结果进一步支持了这样一种观点，即这些潜在的益生菌细菌对宿主没有危害，因为只要这些细菌被聚糖覆盖，它们就不能破坏粘蛋白组织的粘液。
