A hallmark of most cancer cells is an altered metabolism involving a shift to aerobic glycolysis with lactate production coupled with a higher uptake of glucose as the main source of energy. Lactate dehydrogenase (LDH) is key to this shift by catalyzing the formation of lactate by reducing pyruvate with NADH, which also generates NAD( ) that is essential for the continuity of glycolysis. Inhibiting LDH activity has an anti-proliferative effect on cancer cells. It may reverse the resistance of tumor cells to conventional chemo- and radiotherapy. Recent research has renewed interest in LDH as an anticancer drug target. LDH enzymes have three homologous subunits LDHA, LDHB and LDHC. The activity of recombinant rat LDHC was measured by its ability to reduce pyruvate to lactate. The reaction was performed in 25 mM Tris, 100 mM NaCl, pH 7.5 (assay buffer), initiated by addition 50 μL of various concentrations of rrLDHC (diluted by assay buffer) to 50 µL of substrate mixture 1.6 mM beta-NADH and 4 mM sodium pyruvate. The final well serves as a negative control with no rrLDHC, replaced with 50 μl assay buffer. Read at a wavelength of 340 nm in kinetic mode for 5 minutes. The specific activity of recombinant rat LDHC is > 880 pmol/min/µg.