Question

Which compound is involved in reducing levels of homocysteine in the blood?

Cysteine
Adenosine
Serine
N5, N10-methylene tetrahydrofolate
Methionine

Methotrexate inhibits purine synthesis by targeting formation of:
N¹⁰-formyl-tetrahydrofolate from tetrahydrofolate and formate.
Folic acid from PABA and pteridine precursor.
S-adenosylmethionine from methionine.
Tetrahydrofolate from dihydrofolate.

Answer 1

Homocystein level is reduced by vitamin B12 and folate. One of the folate, 5-methyltetrahydrofolate acts as a methyl-group donor in the conversion of homocysteine back to methionine. Thus correct option is N5 N10- methylene tetrahydrofolate

Methotrexate is an antimetabolite drug with that inhibits tetrahydrofolate dehydrogenase and prevents the formation of tetrahydrofolate. Thus correct option is Tetrahydrofolate from dihydrofolate