Investigation of the interaction of trypsin with heparin.

The reversible inhibition of the enzymatic activity of trypsin by heparin was investigated. On the basis of an analysis of the Lineweaver-Burk and Dixon graphs, a noncompetitive nature of the inhibition of the BAPA amidase activity of trypsin by heparin was detected, and the values of Km and Ki were determined, equal to 3.1 . 10(-4) and 3.7-3.9 . 10(-7) M, respectively. A comparison of these values indicates a great affinity of heparin for the enzyme. It was shown that heparin inhibits the BAEE esterase activity of trypsin and at the same time has no inhibiting effect on acetyltrypsin. Considering that the acetylation of trypsin leads to selective blocking of the epsilon-amino groups, it was concluded that the epsilon-amino groups of the lysine residues of the trypsin molecule participate in the interaction with heparin.