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. Author manuscript; available in PMC: 2022 Jan 15.
Published in final edited form as: Arch Biochem Biophys. 2020 Dec 1;697:108702. doi: 10.1016/j.abb.2020.108702

Figure 1. The KMO reaction cycle.

Figure 1.

In the KMO reaction, L-KYN binds to the protein first, then NADPH binds and reduces the FAD followed by NADP+ release, allowing for dioxygen binding. A FAD–superoxide radical pair is likely to be formed and rapidly decays to a peroxy-flavin structure, which will act as the electrophile for L-KYN oxidation. C4a-hydroxy flavin is then dehydrated yielding the oxidised flavin. The final step is 3-HK release, which is also the rate limiting step with a slightly faster rate than the overall turnover number [56].