Pyrroloquinoline quinone (PQQ) was discovered by J.G. Hauge as the third redox cofactor after nicotinamide and flavin in bacteria (although they hypothesised that it was naphthoquinone). Anthony and Zatman also found the unknown redox cofactor in alcohol dehydrogenase and named it methoxatin. In 1979, Salisbury and colleagues as well as Duine and colleagues extracted this prosthetic group from methanol dehydrogenase of methylotrophs and identified its molecular structure. Adachi and colleagues identified that PQQ was also found in Acetobacter.
These enzymes containing PQQ are called quinoproteins. Glucose dehydrogenase, one of the quinoproteins, is used as a glucose sensor. Subsequently, PQQ was found to stimulate growth in bacteria. In addition, antioxidant and neuro-protective effects were also found.

Function:
• As a powerful antioxidant, PQQ protects and increases the functionality of existing mitochondria
  -Slowing mitochondrial aging.
• PQQ also promotes the generation of new mitochondria (Mitochondrial Biogenesis).
  -Increased mitochondria = increased energy production.
• PQQ stimulates production of Nerve Growth Factor (NGF).
  -NGF triggers growth of nerve cells to repair damaged nerves from stroke or other injury.