[Modification of enzyme molecules due to naturally-occurring immunoglobulins linking]

The appearance of circulating enzyme-linked immunoglobulin complexes (E-Ig), that are thought to be formed because of specific interaction between circulating immunoglobulins and normal serum isoenzymes. The presence of E-Ig in an individual is regarded as a benign phenomenon, although the presence of E-Ig may result in altered enzyme activity in serum and interfere with the measurement of isoenzymes, and is thus of diagnostic importance. The present paper deals with the isoenzyme specificities of immunoglobulins isolated from E-Igs and electrophoretically abnormal enzyme components due to E-Igs. The immunoglobulins react with a single isoenzyme, certain isoenzymes only or all the isoenzymes of a given enzyme. E-Igs thus formed are themselves heterogeneous, giving rise to many different electrophoretically abnormal enzyme components.