To investigate the effect of limiting amino acid on plasma homocysteine concentration in rats by adding lysine and threonine to wheat gluten.Methods 32 Wistar rats were fed 25S, 25C, 29G and 29GLT diets with different dietary protein species for 14 days. At the end of the experiment, the rats were sacrificed, and blood and liver samples were subject to biochemical analysis. Results Body weight gain in rats fed with wheat gluten dietary was significantly lower than casein and soybean protein dietary, but the decrease in body weight gain was significantly suppressed by adding lysine and threonine. The plasma homocysteine concentration in rats fed with wheat gluten was significantly lower than casein, however the decrease in wheat gluten group was recovered to the level of 25C and 25S by lysine and threonine. Lysine and threonine also suppressed the plasma S-adenosyl methionine (SAM) activity and liver homocysteine betaine methyltransferase (BHMT) activity, but had no effect on the cystathionine beta synthase (CBS) activity. Plasma homocysteine (Hcy) content did not decrease in the soybean protein group with low methionine.Conclusion The effects of wheat gluten on plasma homocysteine concentration may depend on the contents of amino acid. The high level serine and low level lysine and threonine in wheat pluten may lead to the decrease of plasma Hcy content.