| Q1. Could you give me a layperson's definition of vitamin? |
| To tell the truth, there is no official definition of vitamin. Please refer to the definition provided by US. NIH (in Medical Encyclopedia). Vitamins: a group of substances essential for normal metabolism; growth and development; and regulation of cell function. Vitamins work together with enzymes, co-factors (substances that assist enzymes), and other substances. [ top ]
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| Q2. How did you discover the compound PQQ? |
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| PQQ is an already-known compound. This was discovered by Salisbury et al.
(Texas Univ) in 1979. Afterwards, PQQ was found in animals (meats) and plants (vegetables),
and shown to be vital to rodents. But it has not been considered as a vitamin, becuase the biochemical role of PQQ was unknowm. We found a mouse gene by chance; the gene encods a PQQ-binding enzyme. This finding was the start of our study revealing that PQQ is involved in the lysine degradation pathway. We think PQQ now should be recognized as a vitamin. In other words, we discovered a final proof of a new vitamin PQQ. [ top ]
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| Q3. What kind general functions does PQQ play a role in? What about in humans? |
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| At the molecular level, PQQ is involved in the lysine degradation. We have found a gene for PQQ-dependent enzyme from human as well as from mouse. So, PQQ is also essential to humans. However, we don't know the general "specific function (phenotype)". Please hope future studies. But if I must mention, PQQ is important to keep your health. The PQQ-deprived mice showed slow development, friable skin, fragile blood vessels, reduced immune response, and poor reproductive performance. Please note that these symptoms are in the case of PQQ depletion. We have no idea whethre PQQ positively enhances the development or strengthens the skin, rather its possibility is very low. The symptoms observed in PQQ-deprived mice are likely come from the inhibition of the lysine degradation and/or undiscovered PQQ-dependent pathway(s). So, additional intake of PQQ may have no effect on skin or others, if you get enough of PQQ (see Q7). [ top ]
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| Q4. News accounts say it is believed to play a role in fertility. Is that right? |
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| It is right only in the case of "PQQ-deprived mice". But in the case of humans, we should say it is wrong at present, because humans will not become deficient in PQQ if they take ordinary diets. We don't think that PQQ positively enhances the reproductive performance even in mice. Probably due to shortage of PQQ, pups are likely to be unhealthy in the belly of mothers and after being born. In addition, humans and mice are vastly different in the pregnancy mechanism; mice give birth to 10 or more pups on one occasion. (The number of pups are decreased in the PQQ-deprived mice.) Therefore, in regard to human fertility, we cannot infer from the data of PQQ-deprived mice. [ top ]
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| Q5. News accounts also say it has relation to depression. Is that right? |
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| In one word, that is wrong. We found a PQQ-dependent enzyme by chance when we studied bipolar disorder (manic-depressive illness). That possibly caused a misunderstanding. There is no data suggesting the relevance of PQQ to depression. Lastly, "depression" and "bipolar disorder" are different diseases. [ top ]
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| Q6. What kinds of foods do contain PQQ? |
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| PQQ is mostly contained in common foods; especially, in natto, tea,
papayas, and kiwi fruits, comparatively in large quantities. Because it is not easy to quantify the level of PQQ, only limited kinds of foods have been measured, and the accuracy (reliability) of acquired values is not high. It seems that PQQ is generally included more in vegetables or fruits rather than meat. Please see the table showing the PQQ level of several foods. [ top ]
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| Q7. Do we get enough of PQQ? Should we eat some foods more? |
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| Because PQQ is contained in common foods, probably we get enough of PQQ if we ingest ordinary diets. We think that it is more important to eat many kinds of foods than intaking some specific foods. [ top ]
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| Q8. What would happen if we get an excess of PQQ? |
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| Because there is no PQQ-containing vitamin supplement at present, you cannot take PQQ superfluously. In the future, even if PQQ-containing supplements become available, overtake of PQQ will cause a small effect like other water-soluble vitamins (B group and C). It was reported that the obstacle arose in the function of the kidney when an extremely lot of PQQ was administered to experimental animals. The kidney might be burdened in order to discharge a lot of PQQ in urine. Please note that WHO and every government limit the daily dosages of several vitamins such as A, D, E, and K. [ top ]
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| Q9. How do you know that the body cannot make PQQ itself? |
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| As far as we know, only some bacteria can produce PQQ. Although we cannot declare that PQQ isn't made in our bodies, we think that the possibility is very low. PQQ-producing bacteria have a set of genes for PQQ synthetase, but such genes are not found in the human genome. Considering the fact that mice, which have such genes neither, become PQQ deficiency by PQQ-free diet, humans are unlikely to produce PQQ. [ top ]
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| Q10. Will it be given a new name (like vitamin B13 or something?) |
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| No, we think that the substance should be called "pyrroloquinoline quinone (PQQ)". Several vitamins found late are called by their chemical names, e.g. folic acid, biotin, and pantothenic acid, becuase numbering of vitamins was complicated and caused confusion. Vitamin B13 is orotic acid (orotate), which is not a "true vitamin" because it has been proven to be produced in our bodies. [ top ]
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| Q11. Are there likely to be other undiscovered vitamins? |
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| We have no idea. But, we believe, PQQ is the last redox-cofactor vitamin. The following molecule are known as vitamin-like substances: bioflavonoids (vitamin P), coenzyme Q10 (ubiquinone, CoQ10), etc. We are neuroscientists and do not know why these substances are not accepted as true vitamin. [ top ]
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| Q12. Do you expect PQQ to be included in multi-vitamins or other supplements? |
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| Since PQQ is contained in many kinds of foods, as long as you have usual eating habits, the possibility of PQQ shortage is quite low (ref. Q7). Therefore, you do not need to take PQQ from some supplements. But, PQQ may be scarce in people of extremely unhealthy eating habits and in the patients such as alcohol dependence. Although the proof has nothing at present, it may be important to give PQQ-containing multi-vitamin to such patients. [ top ]
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| Q13. Will you appeal to WHO or somewhere to approve the new vitamin PQQ? |
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| At present, we don't have such a plan. In order for WHO or every government to define the daily nutritional requirements of PQQ (the amount of ingestion a day), research results showing how much PQQ is needs for humans are required. The research requires a quantification assay measuring the PQQ level in human blood or urine; however, the technology is not developed now. PQQ is in the unprecedented situation, because it was identified as a vitmain for the first time in 55 years. The handling of new medical supplies by governments completely differs in this half-century, and we don't understand how PQQ will be dealt with. [ top ]
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| Q14. Where can PQQ be purchased? |
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| For scientific reseachers, PQQ is available from the following chemistry companies. Note that the reagents are only for R&D, not for medicine, foods, cosmetics, etc. PQQ of clinical diagonostic grade is NOT available at present. *Sigma-Aldrich --- cat.no. D7783 *Mitsubishi Gas Chemical Company *Wako Pure Chemical Industries --- cat.no. 16-1708 Sigma's reagent is a synthetic compound, and the others' are refined products from culture medium of a certain bacterium. [ top ]
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| Takaoki Kasahara, Ph.D. (casa@brain.riken.jp) |