酪蛋白磷酸肽副产物中仍含有丰富的功能性多肽，从中回收具有降压活性的血管紧张素I转化酶抑制肽具有废物利用和环境保护的意义。本文在前期研究富集活性肽工艺的基础上，从粗富集产物中进一步分离纯化出具有降压活性的多肽单体，并对单体的分子量、一级序列及其稳定性进行了研究。研究结果表明，以粗富集产物为原料，仅通过阴离子交换树脂及液相制备两步就可获得活性较高的转化酶抑制肽单体P16和P18。P16分子量742.6，序列为GPFPIIV，属首次发现；P18分子量1385.8，序列为FFVAPFPE VFGK。二者均具有较高的耐酸碱性和热稳定性，经体外模拟胃肠消化过程后，发生不同程度的分解，但P16的活性在分解后反而升高12.8%，P18则降低37.5%。推测活性的升高或降低均与活性中心暴露或破坏有关。

By-products of casein phosphopeptide contain abundant functional peptides, from which angiotensin I-converting enzyme (ACE-I) inhibitory peptides with antihypertensive activity can be recycled. This is of significance for utilizing waste and protecting the environment. Based on previous research on technology that accumulates bioactive peptides, the peptide monomers with antihypertensive activity were isolated and purified from crude-enriched products, and the molecular weights of peptide monomers, their primary sequences, and stabilities were studied. The results showed that, using the crude products as raw materials, ACE-I inhibitory peptide monomers with high activity, P16 and P18, could be obtained in just two steps, including anion-exchange chromatography and HPLC. The molecular weight of P16 was 742.6 and its primary sequence was GPFPIIV, which was discovered for the first time. The molecular weight of P18 was 1385.8 and its primary sequence was FFVAPFPEVFGK. Both P16 and P18 possessed high acid-base resistance and thermal stability. Various degrees of decomposition occurred in both peptides in the in vitro gastrointestinal digestion test. Nevertheless, the activity of P16 increased by 12.8%, while that of P18 decreased by 37.5%. Thus, the rise and decline were related to the exposure or destruction of the active centers.

广东省科技计划项目（2012B020312004）