A CYSTEINE-RICH SERINE-PROTEASE INHIBITOR (GUAMERIN-II) FROM THE NON-BLOOD SUCKING LEECH WHITMANIA-EDENTULA - BIOCHEMICAL-CHARACTERIZATION AND AMINO-ACID-SEQUENCE ANALYSIS

A cysteine-rich serine protease inhibitor (Guamerin II) was isolated f rom the non-blood sucking leech Whitmania edentula. The new inhibitor was identified as a low molecular weight (6,012 Da) polypeptide with s ome sequence similarities to antistasin, hirustasin and guamerin. The inhibitor contained 56 amino acid residues with 76.8% sequence similar ity to guamerin, 48.2% to hirustasin and 28.6% to the first domain of antistasin. This new inhibitor was the first completely sequenced seri ne protease inhibitor from a non-blood sucking leech. Analysis of the inhibitor revealed that it was active against neutrophil elastase and chymotrypsin, but had no activity against a variety of other proteases . The P1 reactive site residue was identified as methionine and the re sidues surrounding the P1 sire were hydrophobic amino acids. The prima ry structure of the inhibitor showed no similarity to well-known elast ase inhibitors from leeches such as eglin.