Leukocyte cathepsin G (CLP) and elastase (ELP) from human blood were partially purified, and enzymatic properties of CLP and α2-macroglobulin-CLP complex (α2M-CLP) were studied in comparison with those of ELP and α2M-ELP. Furthermore, some synthetic substrates and synthetic reversible inhibitors for CLP were newly synthesized and specificities for CLP were compared with those of α-chymotrysin. The results obtained were as follows.
1) CLP was extracted with 2M NaClO4 for 1hr, and delipidated by CCl4 after dialysis in tris-HCl buffer (0.1M, pH 7.5) containing 0.5M NaCl. Then, CLP was partially purified by Ultrogel AcA 44 gel chromatography.
2) The amidolytic activity of CLP increased with the addition of NaCl, KCl, MgCl2 and CaCl2 as was that of ELP, while the addition of NaClO4, KSCN and KI enhanced the activity of ELP, but inactivated that of CLP.
3) The amidolytic activity of CLP or α2M-CLP was reduced with the addition of dimethyl sulfoxide in the reaction mixture, whereas that of ELP or α2M-ELP increased.
4) Kinetic parameters of Suc-Ile-Pro-Phe-pNA synthesized by the authors were 1.3mM at Km value and 7.5s-1 at kcat value.
5) Some derivatives of Suc-Tyr-Leu-Phe-pNA were synthesized, and Ki value for CLP, ELP and α-chymotrysin was compared.
