Proteolytic enzymes and biological inhibitors. V. Serological relationship between bovine and swine trypsins and bovine -chymotrypsin.

The serological relationship between bovine and swine trypsins, and bovine α-chymotrypsin has been studied with rabbit antisera at different stages in the immunization period. By using paper electrophoresis to distinguish between the naturally occurring inhibitors and the antienzymes in the γ-globulin fractions, combined with the casein precipitating inhibition test (electrophoretic CPI-test) it was found that at 18 days after immunization the antienzymes inhibited only the homologous enzymes. After an additional 12 and 24 days the anti- bovine trypsin also inhibited swine trypsin and α-chymotrypsin, and anti-swine trypsin inhibited bovine trypsin, while antia-chymotrypsin inhibited only the homologous enzyme. The enzyme inhibition in the heterologous systems was about 1/10 of that in the homologous systems. Similar results were obtained by applying the Kunitz test to isolated γ-globulins. The total trypsin inhibitory activity of the whole anti- bovine trypsin serum increased 50 % from the beginning to the end of the immunization period (tested on bovine trypsin). Using the double diffusion technique, cross precipitation only occurred between anti-bovine trypsin and swine trypsin. Acetyltrypsin (bovine) was affected by the 3 antisera in a way similar to native bovine trypsin. The results are discussed in relation to other reports concerning the serological relationship of animal proteinases.