Measurement of Specific Activity of Dihydrofolate Reductase (DHFR) Enzyme and Determination of Folate Content Extracted from UV-Exposed Stem- Derived Callus of Sunflower (Helianthus annuus L.)

Abstract

The results revealed to the increase of the specific activity of dihydrofolate reductase in stem' callus of sunflower, Heliathus annuus L. exposed to UV(360 nm.) for 5,10 and 15min. with the growth period. The total content of folate increased substantially, whereas 20min decreased activity of dihydrofolate reductase and folate content extracted from callus of different age. The inhibitory effect of folate analogoues aminopterin and trimethoprim, In Vivo and In Vitro on dihydrofolate reductase and folate content of sunflower callus exposed or nonexposed to UV was tested. The results revealed that the exposure of callus for five min. exhibited high level of resistance to trimethoprim and aminopterin. The specific activity of dihydrofolate reductase and the total content of folate partially reserved as a result of radiation compared with non-radiated callus