5,10-methyleneTHF polyglutamate + NADP+ <=> 5,10-methenylTHF polyglutamate + NADPH + H+

The methylenetetrahydrofolate dehydrogenase activity of the trifunctional MTHFD1 enzyme catalyzes the reversible reaction of 5,10-methyleneTHF polyglutamate and NADP+ to form 5,10-methenylTHF polyglutamate, NADPH, and H+. MTHFD1 is cytosolic and occurs as a dimer. The human enzyme has been identified and partially characterized biochemically (Hum et al. 1988); additional reaction details can be inferred from the properties of the well-studied homologous rabbit enzyme (Villar et al. 1985).

三功能甲基四氢叶酸脱氢酶（MTHFD1）的甲基烯四氢叶酸多谷氨酸与辅酶NADP+的可逆反应，催化生成5,10-亚甲基四氢叶酸多谷氨酸、NADPH及质子。MTHFD1存在于细胞质中，以二聚体的形式存在。人源酶已通过生化方法被鉴定并部分表征（Hum等，1988年）；关于该酶的额外反应细节，可从已广泛研究的同源兔酶（Villar等，1985年）的属性中推断出来。