Isolation and characterization of a novel trypsin inhibitor from fresh lily bulbs

A 17-kDa trypsin inhibitor was isolated from fresh lily bulbs with an isolation procedure that involved ion exchange chromatography on DEAE-cellulose, affinity chromatography on Affi-gel blue gel, ion exchange chromatography on SP-Sepharose, and gel filtration by FPLC on Superdex 75. Its N-terminal sequence displayed similarity to a short segment of the sequences of the Populus tremula trypsin inhibitor, a putative trypsin inhibitor from Arabidopsis thaliana and sporamin B from sweet potato. The trypsin inhibitor was adsorbed on DEAE-cellulose, unadsorbed on Affi-gel blue gel, and adsorbed on SP-Sepharose. It dose-dependently inhibited trypsin with an IC (50) value of 1.3 microM. There was a stimulatory effect on macrophage production of nitric oxide. Unlike field bean trypsin inhibitor it did not inhibit [methyl-(3)H]thymidine incorporation by leukemia L1210 cells and MBL2 cells when tested up to 100 microM. In contrast to broad bean trypsin inhibitor, there was no inhibitory effect on HIV-1 reverse transcriptase when lily bulb trypsin inhibitor was tested up to 100 microM. The present report is one of the very few on bulbs in contrast to the voluminous literature on seeds.