Abstract
The Kunitz-type protease inhibitors are the best-characterized family of serine protease inhibitors, probably due to their abundance in several organisms. These inhibitors consist of a chain of ~60 amino acid residues stabilized by three disulfide bridges, and was first observed in the bovine pancreatic trypsin inhibitor (BPTI)-like protease inhibitors, which strongly inhibit trypsin and chymotrypsin. In this review we present the protease inhibitors (PIs) described to date from marine venomous animals, such as from sea anemone extracts and Conus venom, as well as their counterparts in terrestrial venomous animals, such as snakes, scorpions, spiders, Anurans, and Hymenopterans. More emphasis was given to the Kunitz-type inhibitors, once they are found in all these organisms. Their biological sources, specificity against different proteases, and other molecular blanks (being also K+ channel blockers) are presented, followed by their molecular diversity. Whereas sea anemone, snakes and other venomous animals present mainly Kunitz-type inhibitors, PIs from Anurans present the major variety in structure length and number of Cys residues, with at least six distinguishable classes. A representative alignment of PIs from these venomous animals shows that, despite eventual differences in Cys assignment, the key-residues for the protease inhibitory activity in all of them occupy similar positions in primary sequence. The key-residues for the K+ channel blocking activity was also compared.
Highlights
Protease inhibitors (PIs) are proteins or peptides capable of inhibiting the catalytic activity of proteolytic enzymes
In this review we present the protease inhibitors described to date from marine venomous animals, most of which have been obtained from sea anemone extracts, and from Conus species, as well as their counterparts in terrestrial venomous animals, such as snakes, scorpions, spiders, frogs and toads, and bees and wasps
In the Acquired Immunodeficiency Syndrome (AIDS), the HIV protease has become an important therapeutic target leading to the development of several protease inhibitors [199,200], and their use as therapeutic drugs has been associated with a drastic reduction in AIDS morbidity and mortality, the benefits have been compromised by viral mutation and drug-resistance [201]
Summary
Protease inhibitors (PIs) are proteins or peptides capable of inhibiting the catalytic activity of proteolytic enzymes. They are widely distributed in nature and can be found in all kingdoms of cellular life and in viral genomes [1,2]. The PIs are presented according to their biological sources, together with their main characteristics and activities against different proteases Their dual function including potassium channel blocking activity is discussed, followed by the molecular diversity of protease inhibitor compounds
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