Chris Anthony

The active site of the model GDH.

A: The disulphide ring of MDH is replaced by His262 [1, 2]

B: His262 was replaced by Tyrosine [2]

C: View of the 'open' active site of GDH [2]

1. Cozier, G.E. & Anthony, C. (1995). The structure of the quinoprotein glucose dehydrogenase of Escherichia coli modelled on that of methanol dehydrogenase from Methylobacterium extorquens. Biochemical Journal 312, 679-685.
2. Cozier, G.E., Salleh, R.A. & Anthony, C. (1999). Characterisation of the membrane glucose dehydrogenase from Escherichia coli and characterisation of a site directed mutant in which His262 has been changed to tyrosine. Biochem. J.  340, 639-647.
3. James, P.L. and Anthony, C. (2003). The metal ion in the active site of the membrane glucose dehydrogenase of Escherichia coli. Biochim. Biophys. Acta 1467, 200-205.

REVIEWS
4. Anthony, C. & Ghosh, M. (1998). The structure and function of the PQQ-containing quinoprotein dehydrogenases. Progress in Biophysics and Molecular Biology 69, 1-21.
5. Goodwin P M, Anthony C (1998) The biochemistry, physiology and genetics of
PQQ and PQQ-containing enzymes. In: Advances in Microbial Physiology.
(Poole R K eds), 40, 1-80.Academic Press, London.
6. Anthony, C. (2004) The Pyrroloquinoline Quinone (PQQ)-Containing Dehydrogenases. In Zannoni D. (ed): Respiration in Archaea and Bacteria. Vol. 1. Diversity of Prokaryotic Electron Transport Carriers, pp. 203-225. Kluwer Academic Publishers. Printed in The Netherlands.
7. Anthony, C. (2004). The quinoprotein dehydrogenases for methanol and glucose. Archives of Biochemistry and Biophysics 428, 2–9.

Publications on GDH by other important research groups
(Note: much of this work was based on our model GDH described above).

M. Yamada, K. Sumi, O. Adachi, Y. Yamada (1993), Topological analysis of
quinoprotein glucose dehydrogenase in Escherichia coli and its ubiquinone
binding site, J. Biol. Chem. 268, 12812– 12817.

M.D. Elias, M. Tanaka, H. Izu, K. Matsushita, O. Adachi, M. Yamada (2000)
Functions of amino acid residues in the active site of Escherichia
coli pyrroloquinoline quinone-containing quinoprotein glucose dehydrogenase.
J. Biol. Chem. 275, 7321– 7326.

MD. Elias, Satsuki Nakamura, Catharina T. Migita, Hideto Miyoshi, Hirohide Toyama,
Kazunobu Matsushita, Osao Adachi and Mamoru Yamada (2004). Occurrence of a Bound Ubiquinone and Its Function in Escherichia coli Membrane-bound Quinoprotein Glucose Dehydrogenase. Journal of Biological Chemistry 279, 3078 – 3083.

Mamoru Yamada, M D Elias, Kazunobu Matsushita, Catharina T Migita, Osao Adachi (2003). Escherichia coli PQQ-containing quinoprotein glucose dehydrogenase: its structure comparison with other quinoproteins. Biochimica et biophysica acta 1647, 185-92.

Kazuo Kobayashi, Golam Mustafa, Seiichi Tagawa, Mamoru Yamada (2005). Transient formation of a neutral ubisemiquinone radical and subsequent intramolecular electron transfer to pyrroloquinoline quinone in the Escherichia coli membrane-integrated glucose dehydrogenase . Biochemistry. 44, 13567-72.

Golam Mustafa, Catharina T. Migita, Yoshinori Ishikawa, Kazuo Kobayashi, Seiichi Tagawa and Mamoru Yamada (2008).  Menaquinone as Well as Ubiquinone as a Bound Quinone Crucial for Catalytic Activity and Intramolecular Electron Transfer in Escherichia coli Membrane-bound Glucose Dehydrogenase.  Journal of Biological Chemistry 283, 28169–28175.

Sode K, Yoshida H, Matsumura K, Kikuchi T, Watanabe M, Yasutake N, Ito S,
Sano H (1995) Elucidation of the region responsible for EDTA tolerance in PQQ glucose dehydrogenase by constructing Escherichia coli and Acinetobacter calcoaceticus chimeric enzymes. Biochem. Biophys. Res. Commun. 211, 268-273.

H. Yoshida, K. Sode (1996). Thr424 to Asn substitution alters bivalent
metal specificity of pyrroloquinoline quinone glucose dehydrogenase,
J. Biochem. Mol. Biol. Biophys. 1 89– 93.

H. Yoshida, K. Kojima, A.B. Witarto, K. Sode,(1999). Engineering a chimeric
pyrroloquinoline quinone glucose dehydrogenase: improvement
of EDTA tolerance, thermal stability and substrate specificity,
Protein Eng. 12 63– 70.

Goldstein A H, Lester T, Brown J (2003) Research on the metabolic engineering
of the direct oxidation pathway for extraction of phosphate from ore has generated
preliminary evidence for PQQ biosynthesis in Escherichia coli as well as a
possible role for the highly conserved region of quinoprotein dehydrogenases.
Biochem. Biophys. Acta 1647, 266-271.

In 2003 a paper in Nature claimed to demonstrate that PQQ is a vitamin. To me thee were so many misunderstandings in this paper that it was clearly completel wrong so i ignored it. I then read that, on the basis of this paper, Mitsubishi were planning to invest a huge amount of money to produce PQQ as a vitamin. I persuaded Nature that they should publish a refutation which they did (Felton and Anthony, 2005) together with a second refutation of some of the ntritional statements. I contacted Mitsubishi scientists and the following week two of them came from Japan to Southampton to discuss it. They understood perfectly and said that Mitsubishi would continue but sell PQQ as a nutritional supplement. They arranged for me to attend a conference on vitamins in Japan and to visit them at Nigata (Click here for pictures).

At this time a lot was written on Wikipedia that was wrong so I argued there at length. Most of this has now been removed but you can look at the discussion on a separate page (Wikipedia and PQQ)

It is generaly accepted that no mammalian PQQ-containing enzyme (quinoprotein) has been described. If such an enzyme does exist then PQQ would almost certainly be a vitamin [analogous to riboflavin, needed in the diet for production of essential flavoproteins]. 

On a separate page there is discussion of PQQ as a nutritional supplement.

My argument against PQQ as a vitamin can be downloaded as a Word document.

      The following section covers all this material in greater detail.

For a summary go my powerpoint presentation

PQQ is now to be produced as a food supplement by Mitsubishi and sold as a vitamin by Maypro

Mitsubishi Announcement: "On August 15, 2008, Mitsubishi Gas Chemical (MGC) announced that it had received official acceptance from the U.S. Food and Drug Administration (FDA) for its notification of coenzyme pyrroloquinoline quinone (PQQ) as a new dietary ingredient. Having received this acceptance, MGC will begin developing the U.S. market for PQQ as an initial step toward the commercialization of PQQ". Mitsubishi statement.

NPI Center announcement: Highly-Anticipated PQQ (Pyrroloquinoline Quinone) Finally Commercialized As VitaPQQ(TM) From Maypro Industries:
“Hailed as a new vitamin by Nature1, VitaPQQ™ brand PQQ is now available from Maypro for use by vitamin and dietary supplement manufacturers.  The launch of VitaPQQ™ is a critical milestone in a decades-long effort to commercialize Pyrroloquinoline Quinone (PQQ), a newly discovered vitamin that offers significant health benefits due to its vitamin-like activity, cognitive function and antioxidant capacity.  VitaPQQ™ is manufactured utilizing a patented natural fermentation process. “
Announcement by NPI-Center.

A brief history of PQQ
PQQ as coenzyme.    PQQ  (Pyrroloquinoline quinone) was first discovered in the early 1960s as the novel prosthetic group (or coenzyme) of bacterial enzymes (now known as quinoproteins). Methanol dehydrogenase was one of the first of these, and was the enzyme subsequently most investigated [With Len Zatman, I discovered the enzyme in 1964 and published the purification and description of its coenzyme in 1967]. It is responsible for oxidizing methanol to formaldehyde in bacteria that grow on methane or methanol. The structure of this novel co-enzyme was determined by Olga Kennard’s group by X-ray crystallography in Cambridge University in 1979. Other quinoproteins containing PQQ include the enzyme responsible for production of vinegar from ethanol by acetic acid bacteria, and glucose dehydrogenase in (amongst others) enteric bacteria. We published the first high resolution structure of methanol dehydrogenase (using X-ray crystallography) in 1995. The unusual structure has radial symmetry and has been called a ‘propeller structure’ and this structure is shared by all the quinoproteins.
No plants or animals have PQQ-containing enzymes. If they did so then it is likely that PQQ would be a vitamin; quinoproteins having PQQ would be analogous to flavoproteins having riboflavin (vitamin B2).

PQQ as dietary supplement. PQQ is present in tiny amounts in animals and has been shown (mainly by the group of Robert Rucker) to improve growth and reproductive performance in mice fed on chemically-defined diets, but he does not claim that this shows it to be a vitamin.  However, this sort of study has led to speculation that PQQ may eventually be found to be a vitamin for humans.

False claim that PQQ is a vitamin.  Although nutritional experiments have indicated some (unknown) metabolic or nutritional role for PQQ in mammals, it cannot seriously be accepted as a vitamin until an enzyme can be shown to require it as its coenzyme. In 2003 Kasahara and Kato claim to have provided this evidence and announced ‘A new redox-cofactor vitamin for mammals' in the top science journal Nature. This was greeted with enthusiasm -  “The first new vitamin for 55 years”. However, their claim was based on sequence analysis of an enzyme, predicted to be involved in mouse lysine metabolism, which showed that part of the protein has a ‘propeller fold',  which is a feature of all PQQ-dependent dehydrogenases.  What the evidence actually suggests is that their (predicted) protein is an interesting novel protein part of which has a propeller structure; but there is no evidence that it is a PQQ-dependent dehydrogenase. In essence their argument is this: Our mouse protein has a ‘propeller’ structure [true]; All PQQ-containing proteins have a propeller structure [true]; Therefore our protein contains PQQ [false]. This is the equivalent of the well known false argument:  All trees are green; My coat is green; My coat is a tree.
       When I pointed out to the journal Nature that their high reputation was being used to justify investments of millions of dollars in the development of PQQ as a vitamin, they investigated the original paper, agreed with our objections and published our argument against it (Felton & Anthony, Nature Vol. 433, 2005). They also published (alongside ours) a paper by Rucker disagreeing with the conclusions of Kasahara and Kato on nutritional grounds, concluding “that insufficient information is available so far to state that PQQ uniquely performs an essential vitamin function in animals”.  
      It should also be noted that the enzyme which they claim to be involved in lysine breakdown does not occur in mice; it is an irreversible enzyme involved in the opposite process of lysine biosynthesis in yeast. The whole of this part of their paper is biochemical nonsense.

CONCLUSION
Mitsubishi is producing PQQ to market as a nutritional supplement, because they know that the evidence for it being a vitamin is not valid. Maypro, and journalists who like a good story, are selling it as a New  Vitamin VitaPQQ. They quote the original Nature paper but ignore the demonstration of its faultyconclusions that was subsequently  published in Nature.