Inhibition of pyruvate dehydrogenase by methotrexate

The effect of methotrexate (MTX) on the activity of pyruvate dehydrogenase from liver mitochondria and from the crude extract of HeLa cells was studied. the activity of the enzyme from liver mitochondria was 50% inhibited with 800nmoles MTX/mg of protein and the enzyme from vrude extract of HeLa cells was 50% inhibited with only 60 nmoles MTX/mg of protein. The specific activity of the former was 0.75nmoles NAD+ reduced.min-1. meg-1 and the latter 0.48nmoles NAD+ reduced.minmg-1