Thermostable Kunitz trypsin inhibitor with cytokine inducing, antitumor and HIV-1 reverse transcriptase inhibitory activities from Korean large black soybeans

A large number of trypsin inhibitors belonging to various types have been purified from different kinds of legumes. In this study, by using liquid chromatography, a Kunitz type trypsin inhibitor (KBTI) with a molecular weight of 20107.645 Da was purified from Korean large black soybeans. KBTI reduced the proteolytic activities of trypsin and α-chymotrypsin with the activity of ∼ 8520 BAEE units/mg and ∼ 24 BTEE units/mg, respectively. It showed high thermal stability (0–100 °C) as well as stability over a large range of pH values (pH 3–11). Furthermore, KBTI inhibited HIV-1 reverse transcriptase activity with an IC50 value of 0.71 μM and induced the release of pro-inflammatory cytokines such as TNF-α, IL-1β, IL-2 and interferon-γ at the mRNA level. KBTI exerted weak antiproliferative activity toward CNE-2 and HNE-2 nasopharyngeal cancer cells, MCF-7 breast cancer cells, and Hep G2 hepatoma cells. KBTI was destitute of mitogenic, ribonuclease and antifungal activities.