N N H2c—0 P CH N 3 o HCOH OH OH HCOH HCOH CH OH OH HC N I C=O C o Vit B 2 FMN AMP FADN N C NH N C O O H3 C H3 C CH3 HCOH HCOH HCOH H2 C O P OH O O OH O P O O CH3 OH OH N N N N NH2 Vit B2 FMN AMP FAD Ⅲ Ⅱ Ⅰ