Fang Evandro Fei, Ng Tzi Bun
School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong,
Appl Biochem Biotechnol. 2015 Apr;175(8):3828-39. doi: 10.1007/s12010-015-1550-1. Epub 2015 Feb 18.
Nephelium lappaceum L., commonly known as "rambutan," is a typical tropical tree and is well known for its juicy and sweet fruit which has an exotic flavor. Chemical studies on rambutan have led to the identification of various components such as monoterpene lactones and volatile compounds. Here, a 22.5-kDa trypsin inhibitor (N . lappaceum trypsin inhibitor (NLTI)) was isolated from fresh rambutan seeds using liquid chromatographical techniques. NLTI reduced the proteolytic activities of both trypsin and α-chymotrypsin. Dithiothreitol reduced the trypsin inhibitory activity of NLTI at a concentration of 1 mM, indicating that an intact disulfide bond is essential to the activity. NLTI inhibited HIV-1 reverse transcriptase with an IC50 of 0.73 μM. In addition, NLTI manifested a time- and dose-dependent inhibitory effect on growth in many tumor cells. NLTI is one of the few trypsin inhibitors with nitric oxide-inducing activity and may find application in tumor therapy.
红毛丹（学名：Nephelium lappaceum L.），通常被称为“毛荔枝”，是一种典型的热带树木，以其多汁甜美、风味独特的果实而闻名。对红毛丹的化学研究已鉴定出多种成分，如单萜内酯和挥发性化合物。在此，利用液相色谱技术从新鲜红毛丹种子中分离出一种22.5 kDa的胰蛋白酶抑制剂（红毛丹胰蛋白酶抑制剂（NLTI））。NLTI降低了胰蛋白酶和α-糜蛋白酶的蛋白水解活性。二硫苏糖醇在浓度为1 mM时降低了NLTI的胰蛋白酶抑制活性，表明完整的二硫键对其活性至关重要。NLTI抑制HIV-1逆转录酶的IC50为0.73 μM。此外，NLTI对多种肿瘤细胞的生长表现出时间和剂量依赖性抑制作用。NLTI是少数具有诱导一氧化氮活性的胰蛋白酶抑制剂之一，可能在肿瘤治疗中得到应用。
