Lu Y, Bennick A
Faculty of Dentistry, University of Toronto, Canada.
Arch Oral Biol. 1998 Sep;43(9):717-28. doi: 10.1016/s0003-9969(98)00040-5.
Tannins are polyphenolic compounds, widely distributed in plant-based foods, which have harmful effects on animals including humans. Salivary proline-rich proteins (PRPs) may act as a defence against tannins by forming complexes with them and thereby preventing their interaction with other biological compounds and absorption from the intestinal canal. The aim here was to compare the ability of members of the family of human PRPs to form insoluble complexes with tannin and to assess the stability of such complexes under conditions similar to those in the alimentary tract. Basic PRPs (BPRPs), which have no other known biological functions, were very effective in forming insoluble complexes with both condensed tannin and tannic acid. Practically no tannin bound to acidic PRPs (APRPs) and glycosylated PRPs (GPRPs), suggesting that tannin in the diet would not affect their biological activities. There were only small differences in the tannin-precipitating ability of various BPRPs of different sizes or sequences, indicating that, although there is considerable phenotypic variation of PRPs, it is not likely to cause marked individual variation in tannin-binding ability. Tryptic digestion of an APRP led to a marked increase in tannin binding to the resulting proline-rich peptides, supporting observations in other studies that there may be an interaction between the proline-poor N-terminal and the proline-rich C-terminal regions in native APRPs, which inhibits the biological activities of the proteins. Deglycosylation of a GPRP also led to a dramatic increase in tannin-binding ability, showing that the carbohydrate side-chains prevent binding of tannin. Most of the condensed tannin-PRP complexes remained insoluble under conditions similar to those in the stomach and small intestine, supporting the proposal that PRPs act as a defence against tannin.
单宁是多酚类化合物，广泛分布于植物性食物中，对包括人类在内的动物具有有害影响。富含脯氨酸的唾液蛋白（PRPs）可能通过与单宁形成复合物来抵御单宁，从而防止它们与其他生物化合物相互作用以及从肠道吸收。本文的目的是比较人类PRP家族成员与单宁形成不溶性复合物的能力，并评估此类复合物在类似于消化道的条件下的稳定性。基本PRPs（BPRPs）没有其他已知的生物学功能，在与缩合单宁和单宁酸形成不溶性复合物方面非常有效。实际上没有单宁与酸性PRPs（APRPs）和糖基化PRPs（GPRPs）结合，这表明饮食中的单宁不会影响它们的生物学活性。不同大小或序列的各种BPRPs在单宁沉淀能力上只有微小差异，这表明尽管PRPs存在相当大的表型变异，但不太可能导致单宁结合能力出现明显的个体差异。对一种APRP进行胰蛋白酶消化导致单宁与产生的富含脯氨酸的肽的结合显著增加，这支持了其他研究中的观察结果，即天然APRPs中富含脯氨酸的N端和C端区域之间可能存在相互作用，从而抑制了蛋白质的生物学活性。对一种GPRP进行去糖基化也导致单宁结合能力急剧增加，表明碳水化合物侧链会阻止单宁的结合。在类似于胃和小肠的条件下，大多数缩合单宁-PRP复合物仍不溶解，这支持了PRPs可抵御单宁的观点。
