title: Characterization of proteases in guts of Daphnia magna and their inhibition by Microcystis aeruginosa PCC 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.
authors.affiliation: Department of Biological Sciences, Rani Durgavati University, 482001 Jabalpur, India.
authors.forename: Manish K
authors.initials: MK
authors.lastname: Agrawal
authors.forename: Anja
authors.initials: A
authors.lastname: Zitt
authors.forename: Divya
authors.initials: D
authors.lastname: Bagchi
authors.forename: Jürgen
authors.initials: J
authors.lastname: Weckesser
authors.forename: Suvendra N
authors.initials: SN
authors.lastname: Bagchi
authors.forename: Eric
authors.initials: E
authors.lastname: von Elert
mesh_terms: D000818:Animals; D001427:Bacterial Toxins / Q000737:chemistry / Q000633:toxicity*; D002851:Chromatography, High Pressure Liquid; D002918:Chymotrypsin / Q000037:antagonists & inhibitors / Q000378:metabolism; D003621:Daphnia / Q000201:enzymology*; D004591:Electrophoresis, Polyacrylamide Gel; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D046931:Microcystis / Q000737:chemistry* / Q000472:pathogenicity; D010447:Peptide Hydrolases / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism; D014357:Trypsin / Q000378:metabolism
chemical_list: D001427:Bacterial Toxins; D004791:Enzyme Inhibitors; D011506:Proteins; D010447:Peptide Hydrolases; D002918:Chymotrypsin; D014357:Trypsin