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. Author manuscript; available in PMC: 2021 Dec 1.
Published in final edited form as: Curr Opin Chem Biol. 2020 Jul 27;59:93–103. doi: 10.1016/j.cbpa.2020.05.001

Figure 4. Key features of the proposed PQQ biosynthetic pathway and the newly proposed mycofactocin pathway.

Figure 4.

A. The production of one molecule of PQQ requires the participation of at least six proteins, five equivalents of O2, one equivalent of SAM and the participation of an electron donor system to initiate the reductive SAM cleavage. B. The newly proposed redox cofactor mycofactocin (MFT) biosynthetic pathway shares high similarity to PQQ biogenesis. [82,84] In the proposed pathway, MftA, a short peptide, is modified by radical SAM enzyme, MftC, in the presence of a chaperone, MftB. The modified MftA is hydrolyzed by protease, MftE, followed by oxidative deamination and glycosylation. The mature MFT contains a presumed redox-active MFT core that can be reduced to MFTH2.[84]