Is production of protease inhibitors from cyanobacteria nutrient dependent? Comparison of protease inhibitory activities in three species of Oscillatoria isolated from Central India

Abstract

Protease inhibitors are produced by a large number of cyanobacterial genera and their motive and mode of production are largely unknown. The present study showcases a comparative study of three isolates: DL02, DL08 and DL018 of <em>Oscillatoria</em> species collected from Central India, which possessed the same degree of protease inhibitory activities during isolation. These strains were grown under the same nutritional and environmental conditions in the laboratory for many generations, cultured biomasses were extracted, and screened for their inhibitory activity against three major proteases, i.e., trypsin, chymotrypsin and papain using an endpoint assay with casein and kinetic assay using synthetic chromogenic substrates. When cultured under the same conditions, three <em>Oscillatoria</em> strains showed different degrees of protease inhibition against all tested proteases in both the assay systems. <em>Oscillatoria</em> sp. DL08 showed highest inhibition (least IC50 value) against all the enzymes in both endpoint as well as kinetic assays while <em>Oscillatoria</em> sp. DL18 almost lost its protease inhibitory function against tested proteases. Further, papain inhibitory function of <em>Oscillatoria</em> sp. is shown for the first time. The study suggests that production of protease inhibitor(s) may not be entirely dependent on abiotic factors such as nutrient availability, light and temperature, but rather a more complex process having several biotic and abiotic factors working in tandem.