MTX在DNA合成途径的抑制机制。MTX:甲氨蝶呤;台塑:folylpolyglutamate合成酶;MTX-PGs:甲氨蝶呤polyglutamates;DHFR:二氢叶酸还原酶;TS: thymidylate合成酶;FH4: tetrahydrofolate;FH2中:二氢叶酸;10-methylenetetrahydrofolate Methylene-THF: 5;Methyl-THF: 5-methyltetrahydrofolate; dUMP: deoxyurindine-5′-monophosphate; dTMP: deoxythymidine-5′-monophosphate; MTRR: methionine synthase reductase; SHMT: serine hydroxymethyltransferase.