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. 2020 Jun 24;477(12):2313–2325. doi: 10.1042/BCJ20200221

Figure 1. The early (B)Chl biosynthetic steps from PPIX to DV PChlide a.

Figure 1.

(A) Formation of MgPME from PPIX catalyzed by the magnesium chelatase (ChlIDH, Gun4) and the MgP methyltransferase (ChlM). ATP, adenosine triphosphate; ADP, adenosine diphosphate; Pi, inorganic phosphate; SAM, S-adenosine-l-methionine; SAH, S-adenosyl-l-homocysteine. (B) Formation of the isocyclic E ring (highlighted) of (B)Chl is catalyzed by three classes of O2-dependent cyclase: AcsFOx denotes AcsF from oxygenic phototrophs, which requires Ycf54; AcsFAnox denotes AcsF from anoxygenic phototrophs excluding Alphaproteobacteria; and AcsFα denotes alphaproteobacterial AcsF, which requires BciE. e− represents the electron donor to the diiron center of AcsF. International Union of Pure and Applied Chemistry numbering of the relevant macrocycle carbons is indicated.