Carbohydrate-containing derivatives of the trypsin-kallikrein inhibitor aprotinin from bovine organs. I. Modification with lactose, characterization and behaviour of the preparation in vivo.

The trypsin-kallikrein inhibitor aprotinin was modified with lactose. The influence of reactant concentrations, temperature, reaction time and sodium borohydride on the carbohydrate residue content and the inhibiting activity of glycated aprotinin were studied. Glycation of aprotinin neither shifts the pH optimum of the inhibitor-trypsin association reaction nor does it alter the apparent dissociation constant Ki of the complex measured at pH optimum. Glycation by lactose stabilizes aprotinin against denaturation by increased temperature. The distribution of native and modified aprotinin in rat organs after endocardiac injection was studied. Fixation of glycated aprotinin increases 2.5- to 3-fold in liver and decreases 2-fold in kidneys during the observation time (5 min-2 h) compared to native aprotinin.