Cysteine and serine protease-mediated proteolysis in body homogenate of a zooplankter, Moina macrocopa, is inhibited by the toxic cyanobacterium, Microcystis aeruginosa PCC7806

• Published in: Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology 2005-05, Vol.141 (1), p.33-41
• Main Authors: Agrawal, Manish Kumar, Bagchi, Divya, Bagchi, Suvendra Nath
• Format: Article
• Language: English
• Subjects: Animals; Benzoylarginine Nitroanilide - metabolism; Caseins - metabolism; Chymotrypsin; Chymotrypsin - metabolism; Cladocera - metabolism; Cyanobacteria; Cyanobacteria crustacean herbivor interaction; Cyanobacteria–crustacean herbivore interaction; Cysteine Endopeptidases - chemistry; Cysteine Endopeptidases - metabolism; Cysteine protease; Cysteine Proteinase Inhibitors - pharmacology; cysteine proteinases; Inhibitory Concentration 50; Marine; Microcystis; Microcystis - physiology; Moina; Molecular Weight; Pancreatic Elastase - metabolism; Protease inhibitory metabolites; Proteins - drug effects; Proteins - metabolism; Serine Endopeptidases - chemistry; Serine Endopeptidases - metabolism; serine proteinases; Substrate Specificity; Trypsin; Trypsin - metabolism; Zooplankton
• ISSN: 1096-4959; 1879-1107
• DOI: 10.1016/j.cbpc.2005.01.002

The paper describes the characterization of proteases in the whole body homogenate of Moina macrocopa, which can possibly be inhibited by the extracts of Microcystis aeruginosa PCC7806. With the use of oligopeptide substrates and specific inhibitors, we detected the activities of trypsin, chymotrypsin, elastase and cysteine protease. Cysteine protease, the predominant enzyme behind proteolysis of a natural substrate, casein, was partially purified by gel filtration. The substrate SDS–polyacrylamide gel electrophoresis of body homogenate revealed the presence of nine bands of proteases (17–72 kDa).The apparent molecular mass of an exclusive cysteine protease was 60 kDa, whereas of trypsin, it was 17–24 kDa. An extract of M. aeruginosa PCC7806 significantly inhibited the activities of trypsin, chymotrypsin and cysteine protease in M. macrocopa body homogenate at estimated IC 50 of 6- to 79-µg dry mass mL −1. Upon fractionation by C-18 solid-phase extraction, 60% methanolic elute contained all the protease inhibitors, and these metabolites could be further separated by reverse-phase liquid chromatography. The metabolites inhibitory to M. macrocopa proteases also inhibited the corresponding class of proteases of mammalian/plant origin. The study suggests that protease inhibition may contribute to chemical interaction of cyanobacteria and crustacean zooplankton.