Uptake of 5-formyltetrahydrofolate in isolated rat liver mitochondria is carrier-mediated.

摘要: We have characterized the uptake of 5-formyltetrahydrofolate into isolated rat liver mitochondria. Uptake 5-formyltetrahydrofolate, 5-methyltetrahydrofolate and folic acid was linear for first 2 min incubation. 5-Methyltetrahydrofolate were accumulated in mitochondria to 3.7- 4.3-fold, respectively. 5-Formyltetrahydrofolate transport showed a pH optimum at 5.5 saturable with an apparent Km = 2.80 mumol.L-1 Vmax 3.49 pmol.min-1.mg protein-1. inhibited by structural analog and, much lesser extent, methotrexate. not various substrates known mitochondrial transporters, e.g., succinate, malate, citrate, glutamate phosphate, nor sulfhydryl reagent, N-ethylmaleimide. stimulated preloading malate or aspartate. affected proton ionophore carbonyl cyanide 4-trifluoromethoxyphenyl-hydrazone collapsing electrical gradient valinomycin. These results indicate that via carrier-mediated system specific reduced, naturally occurring folates. The folates, once mitochondria, may be converted polyglutamylated forms, which will readily diffuse out