NADPH+H NADP+ HN C-CH HN CH-CH; CH 0 CH H 二氢胸腺嘧啶 胸腺嘧啶 H20 CO,+NH; H,O HO H,N CH-CH H,N-CH,-CH-COOH CH, CH; B-氨基异丁酸 B-脲基异丁酸