Proposed chemical mechanism of mALAS2. (I) Internal aldimine complex, (II) glycine-external aldimine, (III) quinonoid intermediate I, (IV) glycine–succinyl-CoA condensation intermediate, (V) 2-amino-3-ketoadipate intermediate, (VI) enol intermediate, (VII) quinonoid intermediate II, (VIII) ALA-external aldimine. This scheme was originally published in Ref. [12] in the Journal of Biological Chemistry. © The American Society for Biochemistry and Molecular Biology.