Synthesis of rat-liver lactate dehydrogenase and characterization of its mRNA

Rat liver lactate dehydrogenase (LDH) has been synthesized in hepatocytes and in a cell-free translation system. The subunit synthesized in both systems displayed the same electrophoretic mobility upon sodium dodecyl sulfate/polyacrylamide slab gel electrophoresis. Sequence analysis of the subunits translated in vitro and synthesized in vivo indicated N-acetyl-alanyl-alanine for both N termini. Thus, the newly synthesized subunit does not exhibit an amino-terminal extension. The mRNA for the lactate dehydrogenase subunit was exclusively found in free polysomes. A size of 2120 +/- 240 nucleotides was estimated for the mRNA. Only about 50% of these nucleotides are needed to code for the polypeptide chain of the enzyme.