Background and objective: Protease inhibitors (PIs) regulate various cellular processes like cell cycle, differentiation, apoptosis and immune responses. Leguminous seeds are rich sources of protease inhibitors and many novel protease inhibitors have been purified from them. To isolate and purify protease inhibitors from seeds of Sophora japonica, characterize and investigate their anti- microbial activity.
Materials and methods: Protease inhibitors (SJ-pi I and SJ-pi II) were purified to homogeneity by ammonium sulfate precipitation, Ion exchange chromatography and column chromatography. The molecular mass was estimated by size exclusion chromatography and by SDS-PAGE and anti- microbial activity was tested by agar disk diffusion method.
Results: Two protease inhibitors were isolated and purified from Sophora japonica seeds, SJ-pi I and SJ-pi II, with molecular weight of 15.1 and 31 kDa, respectively. Both purified inhibitors were active over a range of pH (6.0-9.0) and showed maximum activity in the temperature range of 30-40°C. They inhibited the growth of three Gram-positive bacteria.
Conclusion: Protease inhibitors were classified as serine protease inhibitors, however further necessary structural investigations need to be carried out so as to group them into specific class of serine protease inhibitors.
Keywords: Protease inhibitors; Sophora japonica; anti-microbial activity; chromatography; leguminous seeds; optimum pH and temperature.