Existence in Human Serum of Cathepsin-Like Enzyme and Its Functional Role
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概要
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In human serum there exists proteinase active in an alkaline medium, namely plasmin and proteinase which are capable to hydrolyze casein, hemoglobin and fibrin in an acidic medium, the optimal pH ranging from 5.0 to 6.0. Proteinase having slightly acidic pH may be considered as a cathepsin-like enzyme, which is to be designated as catheptase.<BR>First of all, addition of potassium cyanide increased catheptase activity but suppressed plasmin activity. Secondly, addition of 1-cysteine markedly activated catheptase activity but decreased plasmin activity. Thirdly, catheptase activity was not suppressed by epsilon aminocaproic acid. The activity was not increased by streptokinase. From the above-mentioned facts, it is certain that there exists in human serum an acidic proteinase different from plasmin.<BR>Catheptase activity in normal subjects was determined to be 34.3±14.1 μg per ml. tyrosine. Determination in 280 patients with various disorders revealed that higher values were seen in hypertension, urticaria, arteriosclerosis, diabetes, nephritis, neoplastic diseases, hematologic disorders such as leukemia, purpura and the like.<BR>The diseases with the lower values comprised liver cirrhosis and old cerebrovascular injury. There was a positive correlation between fibrin degradation products (FDP) and catheptase activity (X<SUP>2</SUP>=8.05, p<0.01).<BR>As to the relation between plasminogen activity and catheptase activity, in patients with urticaria, 25% of 16 cases found a higher titer of FDP. On the other hand, in patients with liver cirrhosis and/or chronic hepatitis, 60% of 17 cases, and in bleeding tendency patients, 60% of 22 cases a higher titer of FDP was observed, respectively.<BR>It was found that the increase in catheptase activity and a high titer of FDP was twice in urticaria patients than that in the patients with other diseases.<BR>From these results, it was concluded that catheptase is involved in fibrinolysis in the initiation of both blood and/or tissue proteinase.
- Japan Society of Clinical Chemistryの論文