Purification and characterization of a lectin with antiproliferative activity toward cancer cells from the dried fruit bodies of Lactarius flavidulus.

The isolation of a dimeric 29.8-kDa lectin (LFL) from dried Lactarius flavidulus fruit bodies is reported herein. The chromatographic procedure utilized comprised anion-exchange chromatography on DEAE-cellulose, cation-exchange chromatography on CM-cellulose, anion-exchange chromatography on SP-Sepharose, and gel filtration by fast protein liquid chromatography on Superdex 75. The hemagglutinating activity of LFL was inhibited by a variety of simple sugars, such as lactose, p-nitrophenyl α-D-glucopyranoside, p-nitrophenyl β-D-glucopyranoside and inositol, and by the polysaccharide inulin. The activity of LFL was stable up to 40°C. There was a precipitous drop in activity when the temperature was elevated to 50°C. Hemagglutinating activity was retained when LFL was exposed to 6.25-12.5 mM HCl and NaOH. The activity was potently inhibited by Fe(2+) and Fe(3+) ions, and slightly inhibited by Al(3+) and Mn(2+) ions. LFL suppressed the proliferation of hepatoma (HepG2) and leukemic (L1210) cells with an IC(50) of 8.90 and 6.81 μM, respectively. It inhibited the activity of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) with an IC(50) of 5.68 μM. However, LFL did not exhibit antifungal activity.