Studies on the Influence of Trasylol on the Partition of Trypsin between the Human Plasma Protease Inhibitors in vitro

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Abstract
The distribution of trypsin between the protease inhibitors of human serum with and without Trasylol was studied in vitro. Trypsin was preferentially bound by .alpha.2-macroglobulin on addition of small amounts of the enzyme to normal serum with and without Trasylol in a molar concentration equal to that of .alpha.2-macroglobulin. On saturation of .alpha.2-macroglobulin, a considerable amount of trypsin was bound by Trasylol even when most of the serum .alpha.1-antitrypsin was in a free form. In reaction mixtures containing small amounts of trypsin, Trasylol was identified in a free form and complex with trypsin-.alpha.2-macroglobulin complex and to a limited extent with trypsin. With larger amounts of trypsin, sufficient to saturate .alpha.2-macroglobulin, increasing amounts of Trasylol were bound to trypsin. The relative amount of Trasylol bound to trypsin-.alpha.2-macroglobulin complexes was now smaller. This was explained by a higher affinity (or binding rate) of Trasylol for trypsin than for trypsin-.alpha.2-macroglobulin complexes. Trypsin-Trasylol complexes showed no signs of dissociation after 5 h incubation at 37.degree. C in serum.