Alcohol pyrroloquinoline quinone

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. 

An alternative biosensor system has been developed by Hart et al. [44] which involves the use of the NAD+-dependent GDH enzyme. The first step of the reaction scheme involves the enzymatic reduction of NAD+ to NADH, which is bought about by the action of GDH on glucose. The analytical signal arises from the electrocatalytic oxidation of NADH back to NAD+ in the presence of the electrocatalyst Meldola s Blue (MB), at a potential of only 0Y. Biosensors utilising this mediator have been reviewed elsewhere [1,17]. Razumiene et al. [45] employed a similar system using both GDH and alcohol dehydrogenase with the cofactor pyrroloquinoline quinone (PQQ), the oxidation of which was mediated by a ferrocene derivative. 

The third case for likely enzymatic generation of an a-cyclopropyl radical or a cyclopropanone equivalent leading to target enzyme destruction is in the oxidation of cyclopropanol by certain bacterial alcohol dehydrogenases which have a novel type of redox coenzyme stoichiometrically bound and required for catalysis. The coenzyme has been termed pyrroloquinoline quinone (PQQ) (174) or methoxatin and the trivial name... 

Dehydrogenases, classified under E.C.1.1., are enzymes that catalyze reduction and oxidation of carbonyl groups and alcohols, respectively I5l The natural substrates of the enzymes are alcohols such as ethanol, lactate, glycerol, etc. and the corresponding carbonyl compounds, but unnatural ketones can also be reduced enantiose-lectively. To exhibit catalytic activities, the enzymes require a coenzyme most of the dehydrogenases use NADH or NADPH, and a few use flavin, pyrroloquinoline quinone, etc. The reaction mechanism of the dehydrogenase reduction is as follows ... 

Quinoproteins constitute a class of dehydrogenases distinct from the nicotinamide-and flavin-dependent oxidoreductases 11691. They use different quinone cofactors to convert a vast variety of alcohols and amines into their corresponding carbonyl products11701. Proteins containing the cofactor pyrroloquinoline quinone (PQQ) (Fig. 16.2-36) form the largest and best-characterized sub-group. 

A number of enzymes which catalyze oxidation reactions, including mammalian lysyl and plasma amine oxidases and bacterial alcohol dehydrogenases, have been determined to utilize pyrroloquinoline quinone (PQQ, methoxatin) as a cofactor (Duine et al., 1987). Substrates of the amine oxidases appear to be activated for a-proton abstraction by formation of a Schiff base with PQQ, fol-... 

Shimao M, Yamamoto H, Ninomiya K et al (1984) Pyrroloquinoline quinone as an essential growth factor for a poly(vinyl alcohol)-degrading symbiont, Pseudomonas sp. VM15C. Agric Biol Chem 48 2873-2876... 

An alternative way of NAD" recycling makes use of a three-enzyme cascade with molecular oxygen as the ultimate oxidant (Scheme 3.30) [339]. As in the methods described above, all the enzymes and cofactors have to be precipitated together. Thus, NADH which is produced by HLADH-catalyzed oxidation of a secondary alcohol is re-oxidized by diaphorase at the expense of pyrroloquinoline quinone (PQQ) [340]. The reduced form of the latter (PQQH2) is spontaneously oxidized by molecular oxygen producing hydrogen peroxide, which, in mm, is destroyed by catalase. 

Matsushita K, Takaki Y, Shinagawa E, Ameyama M, Adachi O (1992) Ethanol oxidase respiratory chain of acetic acid bacteria. Reactivity with ubiquinone of pyrroloquinoline quinone-dependent alcohol dehydrogenases purified from Acetobacter aceti and Gluconobacter suboxydans. Biosci Biotechnol Biochem 56(2) 304-310... 

Shimao M, Ninomiya K, Kuno O, Kato N, Sakazawa C (1986), Existence of a novel enzyme, pyrroloquinoline quinone-dependent polyvinyl alcohol dehydrogenase, in a bacterial symbiont. Pseudomonas sp. strain VM15C , Appl Environ Microbiol, 51, 268-275. 

Shimao M, Onishi S, Kato N, Sakazawa C (1989), Pyrroloquinoline quinone-dependent cytochrome reduction in pol3rvinyl alcohol-degrading Pseudomonas sp. Strain VM 5C Appl Environ Microbiol, 55, 275-278. 

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