AIM: To investigate whether potassium cyanate can inactivate glyceraldehydes 3-phosphate dehydrogenase (GAPDH) and thioltransferase (TTase) in bovine lens. METHODS: Fresh intact bovine lenses were incubated with 100mmol/L potassium cyanate(KCNO) for 7 and 12 days respectively. Then all lens were incubated in 50mmol/L DMEM solution. The proteins in the water-soluble fractions from the normal control and the cyanate-modified lens were extracted. The activity of GAPDH and TTase in the water-soluble fraction after incubation at 37℃ was measured by spectrophotometer. RESULTS: GAPDH activity was significantly lower in the cyanate-modified lens proteins than that of the normal control(P <0.01), and considerably diminished in protein incubated with 100mmol/L potassium cyanate for 12 days. There were statistically significant differences in the activity of TTase between the normal control lenses and the carbamylated lenses incubated for 7 days(P <0.05) and 12 days(P <0.01). However, there was no statistical difference between the samples incubated with 100mmol/L KCNO for 7 and 12 days (P =0.19296). CONCLUSION: This study provides evidence to show carbamylation is able to inactivate GAPDH and TTase in bovine lenses. This may have implications for the susceptibility of lenticular GAPDH and TTase to carbamylation, and also for the research on pathogenesis of cataract.