Characterization of a novel elastase inhibitor from a fan coral.

An acidic hydromethanolic extract of the tropical gorgonian Melithea cf. stormii exhibited anti-elastase activity. From the polypeptidic mixture we isolated and purified to homogeneity a protein with a molecular mass determined at 21,159 Da by Maldi/Tof mass spectrometric analysis. The novel protein of marine invertebrate origin strongly inhibited amidolysis of Suc(Ala) 3pNA by porcine pancreatic elastase (PPE) and was labelled iela melst. The N-terminal aminoacid sequence of its 39-first residues revealed the characteristics of a non-classical Kazal-type domain. Iela melst behaved as a reversible tight-binding inhibitor of PPE. The competitive inhibition followed Cha's mechanism A with an equilibrium dissociation constant, Ki, calculated as 1.5 x 10(-9) M.