Margarethe Gramse

Physiology and Pathophysiology of Neutral Proteinases of Human Granulocytes

The occurence of proteolytic enzymes in polymorphonuclear granulocytes was first demonstrated in 1888 by the famous clinician and biochemist Friedrich von Muller1 who showed that a glycerine extract of fresh pus digests fibrin or coagulated protein at a neutral or weakly alkaline pH. Later on at the end of the last and the beginning of this century further characterization of the enzymes including their serum antiproteases was achieved by German and American scientists2,3,4. However, the neutral proteases then became largely forgotten as the result of the attention paid to the acid-cathepsins of the rabbit leukocyte, a convenient but somewhat misleading cell.

Degradation of human plasma fibrin stabilizing factor XIII subunits by human granulocytic proteinases.

Decreased activity of fibrin stabilizing factor XIII may occur in diseases with enhanced destruction of granulocytes. Haemorrhage and impaired wound healing may result. It has been shown by means of SDS-polyacrylamide gel electrophoresis that the neutral proteinases from human polymorphonuclear granulocytes, the Elastase Like Proteinase (ELP), and the Chymotrypsin Like Proteinase (CLP), are able to digest purified human plasma factor XIII. Both subunits, a and b, are affected at concentrations which might locally or systemically occur under pathophysiological conditions. Higher concentrations are required for the degradation of subunit b. Depending on the proteinases, the concentration used and the time of incubation, numerous split products were formed. To obtain comparable effects, the concentration of CLP had to be about twice that of ELP. Aprotinin had only a slight inhibitory effect on the two leukocyte proteinases. The results presented indicate that factor XIII is degraded and inactivated by granulocytic proteinases, both subunits being altered by these proteinases. Therefore the determination of subunit b may be helpful in differentiating between the proteolytic effect of thrombin which degrades only subunit a, and the granulocyte proteinases.

Degradation of human fibrinogen by chymotrypsin-like neutral protease from human granulocytes

Abstract Plasminogen-free human fibrinogen was degraded by highly purified chymotrypsin-like neutral leukocyte protease, one of the three lysosomal neutral proteases of human polymorphonuclear leukocytes. The resulting fibrinogen split products were investigated for their molecular weight using SDS polyacrylamide gel electrophoresis and for their antigenic determinants using two-dimensional immunoelectrophoresis. These split products were compared to the plasmin-derived fragments D and E and to the granulocyte-elastase-derived fibrinogen degradation products. It was further shown that calcium ions have a protecting effect on the fibrinogen proteolysis caused by the chymotrypsin-like protease.

Alpha-2-Plasmin-Inhibitor Inactivation by Human Granulocyte Elastase

Since the description of the fast reacting α2-plasmin inhibitor (1–3) many efforts were made to investigate its physiological role as a fibrinolysis inhibitor (4–7). It has been shown that plasmin inactivation by this inhibitor is a two step reaction: The first step, a very rapid binding of plasmin, is followed by its slower inactivation. Whereas the first step does not require the active enzyme, the bound plasmin liberates in the second step a small peptide from α2-plasmin inhibitor which comparably occurs during other proteinase inhibitor interactions.