Protein-Linked Glycan Degradation in Infants Fed Human Milk.
Protein-Linked Glycan Degradation in Infants Fed Human Milk.
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DOI：
10.4172/2153-0637.s1-002
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发表时间：
2012-05-01
期刊：
影响因子：
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通讯作者：
Lebrilla C
中科院分区：
文献类型：
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作者：
Dallas DC;Sela D;Underwood MA;German JB;Lebrilla C
许多母乳蛋白质被糖基化。糖基化对于保护生物活性蛋白质和肽片段免遭消化非常重要。蛋白连接聚糖具有多种功能；然而，关于婴儿或成人消化系统中蛋白质相关聚糖降解的信息很少。人类消化酶可以分解膳食二糖和淀粉，但复杂的蛋白连接聚糖降解所需的大多数消化酶在人类消化分泌物和肠壁的外部刷状缘膜中都不存在。事实上，复合碳水化合物在通过胃和小肠的整个过程中保持完整，并且在体外与成人胰腺分泌物或完整的肠刷状缘膜一起孵育时不会被降解。然而，人类胃肠道细菌产生多种糖苷酶，其区域和异头特异性与蛋白连接聚糖结构相匹配。这些细菌降解多种复杂碳水化合物，包括各种蛋白连接聚糖。细菌具有聚糖降解能力，而人类消化系统本身则没有，这表明大多数膳食蛋白相关聚糖的分解都是细菌起源的。除了为结肠中的特定细菌提供食物来源外，人乳中的蛋白连接聚糖还可以充当病原菌的诱饵，以防止宿主的入侵和感染。肠道微生物组的组成对于最脆弱的人类——老年人、免疫功能低下者和婴儿（尤其是早产儿）来说可能特别重要。
Many human milk proteins are glycosylated. Glycosylation is important in protecting bioactive proteins and peptide fragments from digestion. Protein-linked glycans have a variety of functions; however, there is a paucity of information on protein-linked glycan degradation in either the infant or the adult digestive system. Human digestive enzymes can break down dietary disaccharides and starches, but most of the digestive enzymes required for complex protein-linked glycan degradation are absent from both human digestive secretions and the external brush border membrane of the intestinal lining. Indeed, complex carbohydrates remain intact throughout their transit through the stomach and small intestine, and are undegraded by in vitro incubation with either adult pancreatic secretions or intact intestinal brush border membranes. Human gastrointestinal bacteria, however, produce a wide variety of glycosidases with regio- and anomeric specificities matching those of protein-linked glycan structures. These bacteria degrade a wide array of complex carbohydrates including various protein-linked glycans. That bacteria possess glycan degradation capabilities, whereas the human digestive system, perse, does not, suggests that most dietary protein-linked glycan breakdown will be of bacterial origin. In addition to providing a food source for specific bacteria in the colon, protein-linked glycans from human milk may act as decoys for pathogenic bacteria to prevent invasion and infection of the host. The composition of the intestinal microbiome may be particularly important in the most vulnerable humans-the elderly, the immunocompromised, and infants (particularly premature infants).