An Immunochemical Study of D-Amino-Acid Oxidase

Abstract

Both crystalline holo- and apo-enzymes of D-amino-acid oxidase [EC 1. 4. 3. 3] from hog kidneys produced antibodies when they were administrated to rabbits for immuni-zation. The presence of about six antigenic sites in the enzyme was demonstrated from the quantitative precipitin test. The antibodies partially inhibited D-amino-acid oxidase. γG-Immunoglobulin for the polo-enzyme (IgGt1) was further fractionated to fragments. Fragments I and II inhibited the enzyme action partially, while Fragment III did not at all. The type of the inhibition was partially noncompetitive with respect to the substrate. Binding of FAD to the apo-enzyme was not inhibited by these fragments. It was thus concluded that there was no distinct difference in the reactions of these two antibodies with the enzyme, and the effect of the antibodies on the enzyme active site was indirect.