| Abstract: | A C-type lactate dehydrogenase isozyme has been purified to homogeneity from the liver of the Atlantic cod. The enzyme consists of four identical subunits each with a mol. wt of 35,000. Optimum concentrations, Kms, and relative activities were determined for various substrates along with the optimum pH for the reaction with pyruvate and lactate. Glyoxalate, alpha-ketobutyrate, alpha-ketovalerate, and alpha-ketoglutarate were significantly reduced but branched chain alpha-ketoacids were not utilised as substrates. Substrate inhibition was observed for both lactate and pyruvate as is generally found for B-type lactate dehydrogenase isozymes but the lactate optimum concentration and Km more closely resemble the A-type lactate dehydrogenases. |
