ACMSD and cancer: Similarly, the down regulation of 3-HAAO in 19/28 cancers is unlikely to result in impaired formation of QA, as the Km of the enzyme for 3-HAA is even much lower (2–3.6 μM) [3] and especially if ACMSD is expressed in only three cancers (in association with expression of FAMID and TDO2 [73]).