Pyrroloquinoline quinone

Magnusson, O.T. et al., Quinone biogenesis structure and mechanism of PqqC, the final catalyst in the production of pyrroloquinoline quinone, Proc. Natl. Acad. Sci. USA, 101, 7913, 2004. 

Conversion of methanol into formaldehyde by methanol dehydrogenase. A complex array of genes is involved in this oxidation and the dehydrogenase contains pyrroloquinoline quinone (PQQ) as a cofactor (references in Ramamoorthi and Lidstrom 1995). Details of its function must, however, differ from that of methylamine dehydrogenase that also contains a quinoprotein—tryptophan tryptophylquinone (TTQ). 

Ramamoorthi R, ME Lidstrom (1995) Transcriptional analysis of pqqD and study of the regulation of pyrroloquinoline quinone biosynthesis in Methylobacterium extorquens AMI. J Bacteriol Yll 206-211. 

Zayats M, Katz E, Baron R, Willner I. 2005. Reconstitution of apo-glucose dehydrogenase on pyrroloquinoline quinone-functionalized Au nanoparticles yields an electrically contacted hiocatalyst. J Am Chem Soc 127 12400-12406. 

Fructose dehydrogenase (FDH) having pyrroloquinoline quinone (PQQ) as a prosthetic group is an redox enzyme to catalyze the oxidation of fructose. A... 

Fig. 1. Prosthetic groups in oxidases (A FAD B Thio-Tyrosine C NAD(P) + D 6-Hydroxy-DOPA E Methoxanthin (Pyrroloquinoline quinone PQQ) F Tryptophane-Tryptophan quinone)...

Examples of surface-immobilized mediators are electropolymerized azines for electro-oxidation of The extreme form of this approach is formation of biocatalytic monolayer, comprising a surface-bound mediator species that is itself bound to a single enzyme molecule. Katz et al. report a complete cell based on novel architecture at both electrodes (Figure 7). On the anode side, the FAD center of glucose oxidase is removed from the enzyme shell and covalently attached to a pyrroloquinoline quinone (PQQ) mediator species previously immobilized on a gold surface. The GOx apoenzyme (enzyme with active center removed) is reintroduced in solution and selectively binds to FAD, resulting in a PQQ-... 

Pyrroloquinoline quinone (PQQ) (or methoxatin) 6 is a coenzyme, responsible for the oxidation of methanol [7]. It has been found that cyclopropanol 4 inactivates the enzyme from M. methanica [8], the dimeric methanol dehydrogenase and the monomeric enzyme from a Pseudomonas PQQ-dependent methanol dehydrogenase [9] by forming adducts such as 7, through a one-electron oxidation process and the ready ring opening of a cyclopropyloxonium radical, Eq. (3) [8,9]. 

An additional condition may be imposed, even when a cofactor-independent enzyme is used, if a mediator molecule is involved in the electron transfer process, as is often the case with oxidases. Laccases, for example, may employ small-molecule diffusible mediator compounds in their redox cycle to shuttle electrons between the redox center of the enzyme and the substrate or electrode (Scheme 3.1) [1, 2]. Similarly, certain dehydrogenases utiHze pyrroloquinoline quinone. In biocatalytic systems, mediators based on metal complexes are often used. 

Shimao M, Tamogami T, Nishi K, Harayama S (1996) Cloning and characterization of the gene encoding pyrroloquinoline quinone-dependent poly(vinyl alcohol) dehydrogenase of Pseudomonas sp. strain VM15C. Biosci Biotechnol Biochem 60 1056-1062... 

Oxidation by direct H transfer from the a-carbon of alcohols to the pyrroloquinoline quinone (PQQ) cofactor of alcohol dehydrogenases was studied using ab initio quantum mechanical methods <2001JCC1732>. Energies and geometries were calculated at the 6-31G(d,p) level of theory, results were compared to available structural and spectroscopic data, and the role of calcium in the enzymatic reaction was explored. Transition state searches at the semi-empirical and STO-3G(d) level of theory provided evidence that direct transfer from the alcohol to C-5 of PQQ is energetically feasible. 

C. PQQ-Dependent Dehydrogenases (PQQ, Pyrroloquinoline Quinone) Properties of Mediators... 

Pyrroloquinoline Quinone Isomers A Prelude to Studies of PQQ Analogs as Pharmaceuticals... 

In studies of analogs of the redox cofactor pyrroloquinoline quinone (PQQ), synthetic efforts have focused initially on isosteric, isomeric structures that reflect on important mechanisms of electron-transfer catalysis mediated by PQQ. These studies provide insight into the choice of PQQ as an electron-transfer catalyst in nature, and bear directly on pharmaceutical applications of this vitamin-like nutritional factor. 

Steinberg, F.M., Gershwin, M.E., and Rucker, R.B., Dietary pyrroloquinoline quinone growth and immune response in Balb/c mice, ]. Nutr., 124, 744, 1994. 

Zhang, Z., Tillekeratne, L.M.V., Kirchhoff, J.R., and Hudson, R.A., High performance liquid chromatographic separation and pH-dependent electrochemical properties of pyrroloquinoline quinone and three closely related isomeric analogs, Biochem. Biophys. Res. Commun., 212, 41, 1995. 

The antiscurvy (antiscorbutic) activity was called vitamin C, and when its structure became known it was called ascorbic acid. The fat-soluble factor preventing rickets was designated vitamin D. By 1922, it was recognized that another fat-soluble factor, vitamin E, is essential for full-term pregnancy in the rat. In the early 1930s vitamin K and the essential fatty acids were added to the list of fat-soluble vitamins. Study of the human blood disorders "tropical macrocytic anemia" and "pernicious anemia" led to recognition of two more water-soluble vitamins, folic acid and vitamin B12. The latter is required in minute amounts and was not isolated until 1948. Have all the vitamins been discovered Rats can be reared on an almost completely synthetic diet. However, there is the possibility that for good health humans require some as yet undiscovered compounds in our diet. Furthermore, it is quite likely that we receive some essential nutrients that we cannot synthesize from bacteria in our intestinal tracts. An example may be the pyrroloquinoline quinone (PQQ).e... 

Bacteria that oxidize methane or methanol (methylotrophs) employ a periplasmic methanol dehydrogenase that contains as a bound coenzyme, the pyrroloquinoline quinone designated PQQ or meth-oxatin (Eq. 15-51).442 I 1 1 This fluorescent ortfzo-quinone... 

PQQ See Pyrroloquinoline quinone Preproteins 519-522. See also Proenzyme(s) peroxisomal 521 Precursor activation 540 Prenatal diagnosis 26 Prenyl diphosphate (pyrophosphate) 390s Prenylation 402... 

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