eNOS synthesizes NO

Nitric oxide (NO) is produced from L-arginine by the family of nitric oxide synthases (NOS) enzymes, forming the free radical NO and citrulline as byproduct (Janssens et al. 1992). The cofactor tetrahydrobiopterin (BH4) is an essential requirement for the delivery of an electron to the intermediate in the catalytic cycle of NOS.

一氧化氮（NO）由精氨酸（L-arginine）经一氧化氮合酶（NOS）酶家族催化生成，同时产生游离的一氧化氮和瓜氨酸作为副产物（Janssens 等人，1992年）。辅因子四氢生物蝶呤（BH4）对于将电子传递至NOS催化周期中间体是不可或缺的。