The first step of the plant pterin branchis catalyzed by GTPcyclohydrolase I and the first step inthe conversion of chorismate to pABAis mediated in plants by aminodeoxychorismate synthase.

• 除合成过程之外,叶酸在植物体内的运输和区域化、叶酸的分解代谢也是影响叶酸含量的重要因素。