Pyrroloquinoline quinone

Pyrroloquinoline quinone (PQQ) was discovered by Houge as the third redox cofactor after nicotinamide and flavin in bacteria. . Anthony and Zatman also found the unknown redox cofactor in alcohol dehydrogenase and named Metoxatin. In 1979, Salisbury and colleagues as well as Duine and colleagues extracted this coenzyme from methanol dehydrogenase of methylotroph 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 quinoproteins, is used for glucose sensor. Subsequently, PQQ was found to have the growth stimulation effect in bacteria. In addition, antioxidant effect and neuroprotective effect were also found. In 1989, Rucker and colleagues reported that mice deprived of PQQ showed various abnormalities and it was suggested that PQQ might have an important nutritional role also in mammals. In 2003, it was reported that aminoadipic semialdehyde dehydrogenase (AASDH) might also use PQQ as a cofactor, suggesting a possibility that PQQ is a vitamin in mammals. However, there is no direct evidence that AASDH requires PQQ as a cofactor in its enzymatic activity. Rucker and colleagues concluded that insufficient information is available so far to state that PQQ is a vitamin for mammals, although PQQ may be an important biological factor.