PURIFICATION AND PARTIAL CHARACTERIZATION OF AN OSTRICH ALPHA(1)-ANTICHYMOTRYPSIN-LIKE SERUM INHIBITOR

alpha(1)-Antichymotrypsin, a member of the serpins, is the predominant plasma inhibitor of neutrophil cathepsin G. The aim of this study was to purify ostrich alpha(1)-antichymotrypsin and to compare its bioche mical properties with those of other species, Ostrich alpha(1)-antichy motrypsin,vas purified from serum by ammonium sulphate fractionation, QAE-Sephadex C-50 and phenyl-Toyopearl chromatography. N-terminal sequ ence, amino acid composition, molecular mass, isoelectric point and re action with cathepsin G, elastase and chymotrypsin were determined, SD S-PAGE revealed a M-r of 55 000 for ostrich alpha(1)-antichymotrypsin and pI values of 6.8 and 4.1-4.3 were obtained. The amino acid composi tion revealed 444 residues and the N-terminal sequence of the first 20 residues revealed a homology of 30% when compared with several other alpha(1)-antichymotrypsin sequences. Total inhibition of cathepsin G b y ostrich alpha(1)-antichymotrypsin was found at a 4:1 molar ratio of inhibitor to enzyme which was similar to that found for commercial alp ha(1)-antichymotrypsin. Immunological studies highlighted the lack of cross-reactivity between ostrich and human alpha(1)-antichymotrypsin. The study indicated that ostrich alpha(1)-antichymotrypsin-like molecu le exhibited similar properties to human alpha(1)-antichymotrypsin alt hough there were notable differences. (C) 1997 Elsevier Science Ltd.