oncology- molec. biology----? - davedoc

[ArchivalUser]

Young man has ALL that improves after chemotherapy with Methotrexate. Inhibition which of the following enzymes is considered as the beneficial result of this drug?

A. DNA polymerase
B. Adenosine deaminase
C. HGPRT
D. Thymidylate synthase
E. Xanthine oxydase

[ArchivalUser]

D.

[ArchivalUser]

could u explain your answer please? because i dont know the write one. i would go for A knowing that methotrexate inhibits dihydrofolate reductase. thanks

[ArchivalUser]

Methotrexate causes what is known as the "thymineless death." As an analogue of folic acid, methotrexate interferes with de novo purine synthesis.

[ArchivalUser]

Of course, this makes methotrexate (MTX) active in the S phase of the cell cycle, thus affecting rapidly dividing cell.s

[ArchivalUser]

so, methotraxate can inhibit thymidylate synthase (indirectly) besides inhibiting dihydrofolate reductase?

[ArchivalUser]

Yes, I believe that to be the case. By interfering with DHF-to-THF, MTX indirectly inhibits thymidylate synthase's function (synthesis of dTMP).

[ArchivalUser]

thanks

[ArchivalUser]

The answer is D. But there are multiple MA for MTX in cancer and it could also be direct (-) of dTMP synthase other than indirectly depleting dTTP via (-) of DHFR>>>(-) nucleoside thymidine

[ArchivalUser]

Yes, I've read that there are multiple enzymes that MTX targets... I just wasn't sure if thymidylate synthase is one of them. Regardless, it gets inhibited. Thanks, fiteth.