Precipitation and Inhibition of Carboxypeptidase by Specific Antisera

SUMMARY 1. Crystalline bovine carboxypeptidase was used as an antigen in ob- taining rabbit antisera which contained precipitating antibodies. Studies showed that the system contained only a single antibody and a single antigen as judged by quantitative precipitin tests and by observations with the agar diffusion method. 2. The antibodies interacted slowly with the enzyme to produce a non- competitive inhibition since the extent of inhibition was not influenced by substrate concentration. Moreover, competitive inhibitors of carboxy- peptidase of low molecular weight had no influence on the antigen-antibody interaction. 3. At high temperatures (25-39.5’), the inhibition is described by the equation for an interaction of 1 molecule of antibody for each active site of enzyme. At 6.4”, the data are described by an equation where the enzymatic site reacts with 2 molecules of antibody.