Purification of two low-molecular-mass serine proteinase inhibitors from chicken liver

Two serine proteinase inhibitors, designated clTI-1 and clTI-2 were purifie d from livers of chickens to apparent homogeneity by a combination of ethan ol-acetone fractionation, gel filtration and ion-exchange chromatography on CM-cellulose and Mono S columns. The inhibitor clTI-1 is a single polypept ide chain, low-molecular-mass protein (M-r about 6200), very stable to heat and ethanol. It inhibits chicken, porcine and bovine trypsins as well as h uman plasmin. The second protein, lcTI-2 of M-r 17 000 was shown to be a ve ry effective inhibitor of both trypsins and human cathepsin G. Since both i nhibitors are sensitive to arginine modification with phenylglyoxal it is a ssumed that this amino acid residue is present at the P-1 position of the r eactive site peptide bond. The N-terminal amino acid sequence of 28 residue s of clTI-2 (SVDVSKYP STVSKDGRTLVACPRILSPV) revealed a high homology of thi s protein to the third domain of the chicken ovoinhibitor, whereas, the clT I-1 (APPAAEKYYSLPPGAPRYYSPVV) has some sequence identity to a fragment of t he human inter-alpha-trypsin inhibitor. (C) 1999 Elsevier Science B.V. All rights reserved.