绿豆胰蛋白酶抑制剂对蛋白质前体加工酶的抑制活性

Inhibition of proprotein convertases by mung bean trypsin inhibitor

目的:从绿豆中提纯天然的绿豆胰蛋白酶抑制剂(MBTI),并测定了它对前体加工酶的抑制活性。方法:通过硫酸铵沉淀、分子筛层析、离子交换、亲和层析和反相高压液相等一系列层析方法,纯化了MBTI;通过筛选得到两种蛋白质前体加工酶Kexin和Furin的高表达酵母菌株和COS-7细胞,用硫酸铵沉淀和分子筛的方法纯化这两种前体加工酶,并测定和计算MBTI对其的抑制活性。结果:纯化的MBTI在HPLC上洗脱为单峰,在SDS-PAGE中为单一条带。MBTI对Kexin的抑制常数达到3.9×10-9mol/L,对Furin有一定的抑制活性,但是抑制活性较弱。结论:MBTI对于Kexin和Furin两种蛋白前提加工酶都有抑制活性,尤其对Kexin抑制活性明显,如经进一步改造将有望成为理想的蛋白前体加工酶抑制剂。

Objective：To extract the mung bean trypsin inhibitor （MBTI） from mung bean and to study the inhibitory activity of MBTI against proprotein convertases （PCs）. Methods： MBTI was purified to homogeneity by ammonium sulfate precipitation, sequential chromatography of gel filtration, ion exchange, affinity chromatography and HPLC. The high expression strains of 2 PCs, Kexin and Furin, were selected. Kexin and Furin were purified by ammonium sulfate precipitation and gel filtration. The inhibitory activity of MBTI against Kexin and Furin was assayed and the inhibitory constants （Ki） of MBTI against the 2 PCs were calculated by Dixon＇s plot. Results：The purified MBTI showed a single peak on HPLC and a single band on SDS-PAGE. The inhibitory activity of MBTI against Kexin （Ki= 3. 9 ）〈 10^-9 mol/L） was stronger than that against Furin. Conclusion： MBTI can inhibit both Kexin and Furin, especially Kexin, and also can be an ideal inhibitor against PCs after further modification.