Studies on a plasminogen activating system in human milk. I. Isolation of plasminogen activator and proactivator from human milk, and estimation of their molecular weights
Okamoto, U.; Nagamatsu, Y.; Matsumoto, M.; Yamamoto, J.
Nihon Ketsueki Gakkai Zasshi Journal of Japan Haematological Society 37(2): 121-131
1974
ISSN/ISBN: 0001-5806 PMID: 4471908 Document Number: 79945
1. In human milk plasminogen activator and proactivator activities were high; plasminogen activator was higher in colostrum than in mature milk, whereas proactivator was higher in mature milk; high activator activity, but no proactivator, was found in some samples of colostrum. The increase in the fibrolytic activity on fibrin plate was directly proportional to the logarithmic concentration of natural milk activator and streptokinase(SK)-activated activator of plasminogen. The increase in the formed activator activity was also proportional to the logarithm of the amount of SK added. Natural milk plasminogen and SK-activated activator were inhibited equally by trans aminomethyl cyclohexanecarboxylic acid. Milk plasminogen activator was labile in acid and alkaline media, but stable in neutral medium, whereas milk plasminogen proactivator was labile in alkaline but stable in neutral and acid media. Even when heated at 85 deg C for 30 min the proactivator was stable at pH 3.01 to 8.0. Gel filtration indicated that the particle sizes of milk activator and proactivator corresponded to molecular weights of about 80 000 and 105 000, respectively. (From summary.).