<prompt> Which of the following is an inhibitor of dihydrofolate reductase-PhenytoinAlcoholMethotrexateYeast  <response>: Ans. is c i.e., Methotrexate o Methotrexate is folate antagonist : inhibits dihydrofolate reductase DHP Rase - blocking the conversion of dihydrofolic acid to tetrahydrofolic acid which is an essential co-enzyme required for one carbon transfer reactions in de novo purine synthesis and amine acid interconversions. 