Japanese researchers have discovered a new vitamin that has an important role in immune response and fertility in mice. The chemical, pyrroloquinoline quinone (PQQ), may have a similar function in humans, they said.
The team from the Institute of Physical and Chemical Research in Tokyo report that they have found a new molecular function of PQQ, first discovered in 1979, leading them to propose its classification as a new B vitamin.
Researchers fed mice a PQQ-deficient diet and found that they grew slowly, had fragile skin and a reduced immune response, and also had problems reproducing. It is thought that because vitamins that have an important effect on mice usually act in the same way in humans, this vitamin may be vital for humans too.
Writing in this week's issue of Nature, Takaoki Kasahara and Tadafumi Kato identify PQQ's role in degrading the amino acid lysine in mice. They found that PQQ generates an enzyme that is required for the reaction to occur.
They explain that PQQ is acting as a redox cofactor in this reaction, just as nicotinamides and flavins act in other enzyme-catalysed redox reactions. They are classified as vitamins because they must be supplied in the diet.
PQQ is believed to be the first new vitamin to be discovered since 1948, and will join niacin/nicotinic acid (vitamin B3) and riboflavin (vitamin B2), in the B vitamin series. There are 13 other known vitamins, organic compounds required in trace amounts for normal growth and metabolic processes.
PQQ is not normally included in multi-vitamin tablets but can be found in vegetables such as parsley, green peppers and kiwi fruit and some meat.
More research is needed to explain the low fertility in mice and find out if the vitamin has a similar role in humans.