has role is protonated form of has functional parent L-glutamic acid pteridines monocarboxylic acid amide antimetabolite antineoplastic agent dicarboxylic acid immunosuppressive agent antirheumatic drug methotrexate dermatologic drug methotrexate(1-) EC 1.5.1.3 (dihydrofolate reductase) inhibitor abortifacient DNA synthesis inhibitor