Pyrroloquinoline Quinone Chemistry, Biology, and Biosynthesis.

The widely distributed, essential redox factor pyrroloquinoline quinone (PQQ, methoxatin) ( 1 ) was discovered in the mid-1960s. The breadth and depth of its biological effects are steadily being revealed, and understanding its biosynthesis at the genomic level is a continuing process. In this review, aspects of the chemistry, biology, biosynthesis, and commercial production of 1 at the gene level, and some applications, are presented from discovery through to mid-2021.