N5-methyltetrahydrofolate: Homocysteine methyltransferase activity in extracts from normal,malignant and embryonic tissue culture cells |
| |
| Authors: | Hilary Ashe Brian R. Clark Fred Chu Dorothy N. Hardy Barbara C. Halpern Richard M. Halpern Roberts A. Smith |
| |
| Affiliation: | Contribution number 3276 from the Departments of Chemistry, Medicine and the Molecular Biology Institute, University of California, Los Angeles, Ca. 90024 USA |
| |
| Abstract: | Malignant cells (J111, L1210, W-256) and human embryonic cells (FL) are unable to survive and grow when homocystine replaces methionine in tissue culture media containing excess vitamin B12 and folic acid. Extracts of these same cells when grown in media containing methionine and more than adequate vitamin B12 and folic acid have diminished N5-methyltetrahydrofolate: homocysteine methyltransferase activities in the absence of added cyanocobalamin when compared with extracts of normal cells (adult rat thymus and liver fibroblasts). Extracts of human monocytic leukemia (J111) and human amnion cells (FL) have normal enzymatic activity in the presence of added cyanocobalamin whereas the rodent malignant cells (W-256 and L1210) have abnormally low activity in the absence or presence of added vitamin B12. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
