Characterization of proteases in guts ofDaphnia magnaand their inhibition byMicrocystis aeruginosaPCC 7806

Abstract

Many cyanobacteria produce peptides that inhibit mammalian proteases. The hypothesis that inhibitors of mammalian proteases produced by cyanobacteria also interfere with digestive proteases of natural cladoceran grazers was tested by comparing the effects of cyanobacterial protease inhibitors on digestive proteases from Daphnia magna and on commercially available bovine proteases. The major digestive proteases of D. magna are trypsins and chymotrypsins, which differ from those of bovine origin in substrate specificity and susceptibility to synthetic inhibitors. An extract from Microcystis aeruginosa strain PCC 7806 inhibited both types of D. magna proteases. Subsequent fractionation of the extract by high-performance liquid chromatography indicated that several inhibitors are produced by M. aeruginosa that differ in their specificity for the trypsins and chymotrypsins of D. magna. Two fractions differed in their inhibitory effect on proteases of D. magna and bovine origin; therefore, assessment of the impact of cyanobacterial protease inhibitors on natural communities requires the use of digestive proteases from ecologically relevant grazers.

Inducible tolerance to dietary protease inhibitors inDaphnia magna

“…This suggests that cyanobacterial trypsin and chymotrypsin inhibitors constitute an antiherbivore defence that interferes with major digestive proteases in D. magna. In D. magna grown on the green alga S. obliquus, nine different proteases have been distinguished using zymograms (Von Elert et al, 2004), and five proteases ranging from 22 to 75kDa were identified as trypsins through the use of synthetic inhibitors (Agrawal et al, 2005). Here, effects of the synthetic inhibitor chymostatin and the cyanobacterial chymotrypsin inhibitors cyanopeptolin 954 and nostopeptin BN920 reveal that the remaining three proteases in D. magna with a molecular mass ranging from 16 to 24kDa are chymotrypsins.…”

“…have been shown to inhibit trypsin activity in crude extracts of the cladocerans Moina macrocopa (Agrawal et al, 2001), D. magna (Rohrlack et al, 2003;Agrawal et al, 2005) and Daphnia sp. (Blom et al, 2006).…”

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

“…These protease inhibitors have shown to cause inhibition of digestive proteases belonging to a variety of classes and hence can be related to subacute toxicity (Rohrlack et al 2003, Agrawal et al 2005a, b, Agrawal 2010). The present study shows that while grown under similar conditions and nutrients in vitro for many generations, the three isolates of Oscillatoria differed in their protease-inhibiting capabilities despite of similar protease inhibitory potential at the time of harvest from their natural environment.…”

“…All the three extracts were pooled, dried under vacuum and redissolved in 1 ml of 50 % methanol. This extract was used as a source of protease inhibitors from cyanobacteria (Agrawal et al 2005a). …”

“…Though looks simple, the consequences of protease inhibition may lead to various metabolic problems as proteases have a wide presence in the living world. Dysregulation and/or dysfunction of proteases may lead to conditions such as cardiovascular and inflammatory diseases, cancer, osteoporosis and neurological disorders (Turk 2006) apart from the regular digestion impairment in lower animals, i.e., crustaceans (Agrawal et al 2005a).…”