Abstract
An anti-acetylated lactate dehydrogenase (LD) B4 anti-serum was prepared from a New Zealand white male rabbit. This anti-serum formed soluble LD and antibody complexes with non-acetylated LD B4 molecules without inhibiting the LD activity.
This property was also found in other LD isoenzymes containing B subunit in their molecules. Changes of electrophoretic mobility towards the cathodic side were observed in these LD antibody complexes, and free and bound LD isoenzymes were completely separated and could be quantitated by densitometric analysis. These soluble complexes were completely precipitated by the addition of anti-rabbit immunoglobulin G and the free LD activity was clearly measured by the assay of remaining activity in the centrifugal supernatant.
Employing these two separating methods, i. e., the electrophoretic and the immunological method, the equilibrium constant (K) and the heterogeneity index (a) of the antibody for each LD isoenzyme were measured by Sips plot analysis. The antibody showed a high affinity to LD isoenzymes and a different heterogeneity index for each LD isoenzyme. These findings should be useful for the analysis of enzyme linked immunoglobulin appearing in human sera.
