Quinones methanol dehydrogenase

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). 

C. Anthony, M. Ghosh, and C.C. Blake, The structure and function of methanol dehydrogenase and related quinoproteins containing pyrrolo-quinoline quinone. Biochem. J. 304, 665-674 (1994). 

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]. 

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... 

When FI is replaced by PQQ (pyrroloquinolinequinone), a novel heterocyclic o-quinone cofactor that was first isolated and identified from methanol dehydrogenase of methylotrophic bacteria in 1979 [68], the photochemical oxidation of benzyl alcohols occurs efficiently without HC104 in MeCN [69] ... 

ZnS colloids were also used by Kuwabata et al. to photoreduce C02 to formate [130]. In this system, the ZnS colloids also reduced pyrroloquinoline quinone which served as an electron mediator to the enzyme, methanol dehydrogenase, which could then reduce formate to methanol. In C02-saturated aqueous solution at pH 7 and under far-UV (280nm) illumination, quantum efficiencies of 7% and 6% were achieved for formate and methanol, respectively. 

PYRROLO-QUINOLINE QUINONE (PQQ) THE PROSTHETIC GROUP OF METHANOL DEHYDROGENASE... 

Zheng, Y-J., and Bruice, T. C., 1997, Conformation of coenzyme pyrroloquinoline quinone and role of Ca in the catalytic mechanism of quinoprotein methanol dehydrogenase. Proc. Natl. Acad. Set 94 11881911886. 

Some enzymes use other cofactors, e.g., pyrroloquinoline quinone (methoxatin). which has been found in methanol dehydrogenase and several other bacterial dehydrogenases in recent years325. 

Pyrrolo quinoline quinone, PQQ 2,7,9-tricar-boxy-li/-pyrrolo [2,3-/ quinoline-4,5-dione, the cofactor of methanol dehydrogenase (EC 1.1.99.8) from Hyphomicrobium X and Melhylophilus methy-lotrophus, and of glucose dehydrogenase (EC 1.1.99.17) from Acinebacter cakoaceticus. [J. A. Duine et al. Eur. J.Biochem. 108 (1980) 187-192]... 

Westerling J, Frank J, Duine JA (1979) The prosthetic group of methanol dehydrogenase from Hyphomicrobium X electron spin resonance evidence for a quinone structure. Biochem Biophys Res Commun 87 719-724... 

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