EFFECT OF THE BUFFER CONCENTRATION ON THE SEPARATION OF LACTATE-DEHYDROGENASE ISOENZYMES FROM DIFFERENT SOURCES BY ELECTROPHORESIS

The separation of lactate dehydrogenase isoenzymes by zone electrophoresis using cellulose acetate strips as support was dependent on the concentration of the buffer used (5 mM and 50 mM, pH 7.4) and on the source of the material (chicken liver or guinea-pig liver). In three different 5 mM buffer systems, pH 7.4 (phosphate, veronal and Tris-HCl) the four lactate dehydrogenase isoenzymes present in chicken liver cytosol: M3H, M2H2, MH3 and H-4 were resolved into four separated bands. M3H and M2H2 isoenzymes migrated towards the cathode whereas the other two isoenzymes showed anodic mobilities. In 50 mM buffers, pH 7.4 all enzyme activity appeared as a single band with anodic mobility similar to that of H-4. Guinea-pig liver isoenzymes were well resolved in both buffer conditions and appeared as five bands with anodic mobilities. The different behaviour of the lactate dehydrogenase isoenzymes in 5 mM and 50 mM buffers can not be assigned to ionic strength effects but it may explained by assuming the binding of buffer anions to the different isoenzymes. The binding would increase with the molar concentration of the buffer and reduce charge differences among the isoenzymes to different extents depending on the source of the enzyme, chicken or guinea-pig liver.