Biochemical basis of different sensitivity to methotrexate in Daucus carota and Oryza sativa cell cultures.

The biochemical basis of the different sensitivity to methotrexate of Daucus carota and Oryza sativa cell cultures has been investigated. Carrot cells have a dihydrofolate reductase activity about ten times higher than rice cells. In addition, they show a lower uptake rate of the inhibitor. No relevant differences have been found in the Km value for dihydrofolate of the two enzymes and in the degree of inhibition of their activity by methotrexate