Substitution of Glutamine by Glutamate and Alanyl-glutamine to Reduce Ammonia Production in Transgenic Rice Cell Cultures

초록

Human cytotoxic T-lymphocyte antigen 4-immunoglobulin (hCTLA4Ig) was produced in transgenic rice cells. In this system, inducible RAmy3D promoter was used to produce the target protein. Cell death was occurred in production phase because RAmy3D promoter system should be induced by sugar starvation. Glutamine was added as a nitrogen source. Supplement of glutamine enhanced cell viability during production phase. However, ammonia formed from glutamine metabolism inhibited cell growth and production of target protein. When glutamine was added at different concentrations (0, 6, 12 mM) to the medium, it was found that ammonia level was increased and hCTLA4Ig production was decreased at 12 mM. To reduce ammonia, glutamate and alanyl-glutamine were used as the substitute for glutamine [1, 2]. As expected, ammonia level was decreased in medium supplemented with glutamate compared to that with glutamine. Alanyl-glutamine, alanine, glutamine as well as both alanine and glutamine were added at the same concentration. Cell viability was maintained at a high level in culture with glutamine, and maximum hCTLA4Ig production was observed in culture with alanine. In conclusion, it was found that the reduction of ammonia production and enhanced cell viability could be obtained by the substitution of glutamine in transgenic rice cell cultures