Physiologic importance of pyrroloquinoline quinone.

0-quinone cofactors derived from tyrosine and tryptophan are involved in biological reactions that range from oxidative deaminations to free-radical-related redox reactions. Among these cofactors, pyrroloquinoline quinone (PQQ) has excited interest because of its presence in foods, unusual chemical properties and role as a growth-promoting factor in animals. Oral supplementation of PQQ in the nmol/g-diet range has been shown to improve B- and T-cell responsiveness to mitogens, mitochondrial function and reproductive outcome in mice. PQQ is easily absorbed and efficiently taken up by cultured cells. Consequently, a case can be made that PQQ may have physiological importance in animals.