Purification and characterization of a novel RNase with antiproliferative activity from the mushroom Lactarius flavidulus.

A 14.6-kDa RNase, with a pH optimum of 5.5 and a temperature optimum of 70 °C, was isolated from dried fruiting bodies of the edible mushroom Lactarius flavidulus. The purification procedure involved, in succession, ion exchange chromatography on DEAE-cellulose, CM-cellulose and SP-Sepharose, and finally FPLC-gel filtration on Superdex 75. The RNase was adsorbed on all three ion exchangers. The ranking of its activity toward various polyhomoribonucleotides was poly(C) > poly(G) > poly(A) > poly(U). It suppressed proliferation of HepG2 cells and L1210 cells with an IC₅₀ of 3.19 μM and 6.52 μM, respectively. It also inhibited the activity of HIV-1 reverse transcriptase with an IC₅₀ of 2.55 μM.