Summary
Two water-insoluble derivatives of trypsin, one prepared by coupling polytyrosyl trypsin
to diazotized p-amino-phenylalanine-leucine copolymer (IPTT), the other by coupling
trypsin to ethylene maleic anhydride copolymer (IMET), quickly compromise the clotting
of fibrinogen by thrombin, as does native trypsin. When used in equivalent caseinolytic
or esterolytic activity IMET is much more potent than IPTT. The effects, temperature
and concentration dependent, are blocked by trypsin inhibitors. Clotting kinetics
are far more affected than the ultimate fibrin yield obtained by thrombin. Marked
impairment of clottability is associated with cleavage of 1-2 peptide bonds of the
fibrinogen molecule. The early changes are paralleled by release of very small amounts
of TCA-soluble tyrosine-containing fragments, and associated with the appearance in
the ultracentrifuge of a small amount of a fast sedimenting material. The electrophoretic
mobility of the altered fibrinogen remains uniform, but it is significantly slower
than the original intact fibrinogen. Fibrinogen that is exposed to the water-insoluble
trypsin derivatives for relatively short time intervals will under certain conditions
clot spontaneously, indicating that the trypsin splits inter alia the same bonds cleaved
by thrombin. The differences between IPTT and IMET in their actions on fibrinogen
are attributed to the different nature of the carrier to which trypsin is attached
in these water-insoluble derivatives.