NEW ASPECTS OF LACTATE-DEHYDROGENASE ISOE NZYME PATTERN IN THE SERUM OF PIGS AT SLAUGHTER

In the article we describe lactate dehydrogenase - (LD) (EC 1.1.1.27) isoenzyme pattern detected in the sera of pigs at slaughter. The patte rn was different from that of normal serum (Fig 1) and was characteriz ed by the occurrence of an extra LD-fraction in the cathodic site of L D4 (Fig. 2). This fraction was unusual due to its unwillingness to sep arate by native polyacrylamide gel electrophoresis (PAGE) and took sha pe of a diffuse zone. The presence of the extra LD-zone caused a propo rtional decrease in quantitative distribution of the other LD forms, e specially LD1 to LD3, in slaughtered pig sera (Tab. I). We examined th e homogeneity of an apparent LD5-fraction using gel isoelectric focusi ng (IEF). We found out that after separation in a gradient of pH (3-9) two to three new extra bands with LD activity appeared in the area wi th relatively high pH value (pH 9) (Fig. 3). Their localization in the gradient of pH was greatly different from that of true LD molecules, the latter being situated in more acidic area. It is obvious from the finding described above that the diffuse LD-zone, detected in the seru m of pigs at slaughter by native PAGE, was in no case a homogeneous pr otein. Consequently, it eliminates a possibility that the extra LD fra ction reflects an increased LD5 activity in serum of affected animals. On the contrary, the IEF showed that the diffuse LD-zone consisted of two to three electrophoretically distinct proteins with relatively hi gh pI values. As these proteins differed in their electrophoretic prop erties from the true LD isoenzymes we denoted them LD-like proteins. A n origin of the unusual LD-like proteins detected in the serum of pigs at slaughter remains unknown for us for the time being.