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 Oscillatoria 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 Oscillatoria strains showed different degrees of protease inhibition against all tested proteases in both the assay systems. Oscillatoria sp. DL08 showed highest inhibition (least IC50 value) against all the enzymes in both endpoint as well as kinetic assays while Oscillatoria sp. DL18 almost lost its protease inhibitory function against tested proteases. Further, papain inhibitory function of Oscillatoria 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.
Highlights
The diverse physiologies of cyanobacteria serve as an excellent base for production of secondary metabolites, including toxins and enzyme inhibitors (Namikoshi and Rinehart 1996; Harada 2004; Gademann and Portmann 2008)
The present study showcases a comparative study of three isolates: DL02, DL08 and DL018 of Oscillatoria species collected from Central India, which possessed the same degree of protease inhibitory activities during isolation
No significant difference was found among the three cyanobacterial extracts, ensuring that the protease inhibitory potential was statistically similar in all three cyanobacteria
Summary
The diverse physiologies of cyanobacteria serve as an excellent base for production of secondary metabolites, including toxins and enzyme inhibitors (Namikoshi and Rinehart 1996; Harada 2004; Gademann and Portmann 2008). The most pronounce enzyme inhibitors are the inhibitors of proteases. Int Aquat Res (2014) 6:211–220 depsipeptides produced by cyanobacteria have the ability to act as protease inhibitors (Radau 2000; Welker and von Dohren 2006). Protease inhibitors have been isolated from a variety of freshwater cyanobacterial blooms and mats, i.e., Microcystis (Agrawal et al 2001), Lyngbya (Matthew et al 2007), Nostoc sp. A wide range of proteases has been shown to be inhibited by crude extract or purified compounds from cyanobacteria including Oscillatoria. Compounds from Oscillatoria have shown to inhibit major serine protease family member enzymes, i.e., trypsin (Itou et al 1999), chymotrypsin (Fujii et al 2000), elastase (Shin et al 1995) and plasmin (Shin et al 1996)
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