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The oxidative fermentation of ethanol in Gluconacetobacter diazotrophicus is a two-step pathway catalyzed by a single enzyme: alcohol-aldehyde Dehydrogenase (ADHa).

Gómez-Manzo S, Escamilla JE, González-Valdez A, López-Velázquez G, Vanoye-Carlo A, Marcial-Quino J, de la Mora-de la Mora I, Garcia-Torres I, Enríquez-Flores S, Contreras-Zentella ML, Arreguín-Espinosa R, Kroneck PM, Sosa-Torres ME - Int J Mol Sci (2015)

Bottom Line: The oxidation of ethanol to acetic acid of this organism takes place in the periplasmic space, and this reaction is catalyzed by two membrane-bound enzymes complexes: the alcohol dehydrogenase (ADH) and the aldehyde dehydrogenase (ALDH).We present strong evidence showing that the well-known membrane-bound Alcohol dehydrogenase (ADHa) of Ga. diazotrophicus is indeed a double function enzyme, which is able to use primary alcohols (C2-C6) and its respective aldehydes as alternate substrates.Moreover, the enzyme utilizes ethanol as a substrate in a reaction mechanism where this is subjected to a two-step oxidation process to produce acetic acid without releasing the acetaldehyde intermediary to the media.

View Article: PubMed Central - PubMed

Affiliation: Laboratorio de Bioquímica-Genética, Instituto Nacional de Pediatría, S.S. Mexico City 04530, Mexico. saulmanzo@ciencias.unam.mx.

ABSTRACT
Gluconacetobacter diazotrophicus is a N2-fixing bacterium endophyte from sugar cane. The oxidation of ethanol to acetic acid of this organism takes place in the periplasmic space, and this reaction is catalyzed by two membrane-bound enzymes complexes: the alcohol dehydrogenase (ADH) and the aldehyde dehydrogenase (ALDH). We present strong evidence showing that the well-known membrane-bound Alcohol dehydrogenase (ADHa) of Ga. diazotrophicus is indeed a double function enzyme, which is able to use primary alcohols (C2-C6) and its respective aldehydes as alternate substrates. Moreover, the enzyme utilizes ethanol as a substrate in a reaction mechanism where this is subjected to a two-step oxidation process to produce acetic acid without releasing the acetaldehyde intermediary to the media. Moreover, we propose a mechanism that, under physiological conditions, might permit a massive conversion of ethanol to acetic acid, as usually occurs in the acetic acid bacteria, but without the transient accumulation of the highly toxic acetaldehyde.

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Chromatogram obtained from the analysis of the products in the final reaction by GC-MS. The purified ADHa enzyme from Ga. diazotrophicus was suspended in potassium phosphate buffer, pH 6.0. Potassium ferricyanide was used as an electron acceptor, and ethanol was used as the initial substrate.
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ijms-16-01293-f002: Chromatogram obtained from the analysis of the products in the final reaction by GC-MS. The purified ADHa enzyme from Ga. diazotrophicus was suspended in potassium phosphate buffer, pH 6.0. Potassium ferricyanide was used as an electron acceptor, and ethanol was used as the initial substrate.

Mentions: The purified ADHa enzyme was incubated with potassium ferricyanide as an electron acceptor and ethanol was used as an initial substrate in a hermetically closed tube. After the reaction was completed, an aliquot of the final reaction mixture was injected in the JEOL/JM-AXSOSHA instrument, previously equilibrated. The reaction products are shown in Figure 2. There we observe a mixture of ethanol (initial substrate) and the acetate (final product) with retention time of 2.73 and 4.29 min, respectively. However, we do not observe the presence of acetaldehyde (1.66 min) as a final product of the reaction catalyzed by the enzyme ADHa. The retention times in the final reaction mixture are in agreement with those obtained for ethanol and acetate, used as standards.


The oxidative fermentation of ethanol in Gluconacetobacter diazotrophicus is a two-step pathway catalyzed by a single enzyme: alcohol-aldehyde Dehydrogenase (ADHa).

Gómez-Manzo S, Escamilla JE, González-Valdez A, López-Velázquez G, Vanoye-Carlo A, Marcial-Quino J, de la Mora-de la Mora I, Garcia-Torres I, Enríquez-Flores S, Contreras-Zentella ML, Arreguín-Espinosa R, Kroneck PM, Sosa-Torres ME - Int J Mol Sci (2015)

Chromatogram obtained from the analysis of the products in the final reaction by GC-MS. The purified ADHa enzyme from Ga. diazotrophicus was suspended in potassium phosphate buffer, pH 6.0. Potassium ferricyanide was used as an electron acceptor, and ethanol was used as the initial substrate.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4307304&req=5

ijms-16-01293-f002: Chromatogram obtained from the analysis of the products in the final reaction by GC-MS. The purified ADHa enzyme from Ga. diazotrophicus was suspended in potassium phosphate buffer, pH 6.0. Potassium ferricyanide was used as an electron acceptor, and ethanol was used as the initial substrate.
Mentions: The purified ADHa enzyme was incubated with potassium ferricyanide as an electron acceptor and ethanol was used as an initial substrate in a hermetically closed tube. After the reaction was completed, an aliquot of the final reaction mixture was injected in the JEOL/JM-AXSOSHA instrument, previously equilibrated. The reaction products are shown in Figure 2. There we observe a mixture of ethanol (initial substrate) and the acetate (final product) with retention time of 2.73 and 4.29 min, respectively. However, we do not observe the presence of acetaldehyde (1.66 min) as a final product of the reaction catalyzed by the enzyme ADHa. The retention times in the final reaction mixture are in agreement with those obtained for ethanol and acetate, used as standards.

Bottom Line: The oxidation of ethanol to acetic acid of this organism takes place in the periplasmic space, and this reaction is catalyzed by two membrane-bound enzymes complexes: the alcohol dehydrogenase (ADH) and the aldehyde dehydrogenase (ALDH).We present strong evidence showing that the well-known membrane-bound Alcohol dehydrogenase (ADHa) of Ga. diazotrophicus is indeed a double function enzyme, which is able to use primary alcohols (C2-C6) and its respective aldehydes as alternate substrates.Moreover, the enzyme utilizes ethanol as a substrate in a reaction mechanism where this is subjected to a two-step oxidation process to produce acetic acid without releasing the acetaldehyde intermediary to the media.

View Article: PubMed Central - PubMed

Affiliation: Laboratorio de Bioquímica-Genética, Instituto Nacional de Pediatría, S.S. Mexico City 04530, Mexico. saulmanzo@ciencias.unam.mx.

ABSTRACT
Gluconacetobacter diazotrophicus is a N2-fixing bacterium endophyte from sugar cane. The oxidation of ethanol to acetic acid of this organism takes place in the periplasmic space, and this reaction is catalyzed by two membrane-bound enzymes complexes: the alcohol dehydrogenase (ADH) and the aldehyde dehydrogenase (ALDH). We present strong evidence showing that the well-known membrane-bound Alcohol dehydrogenase (ADHa) of Ga. diazotrophicus is indeed a double function enzyme, which is able to use primary alcohols (C2-C6) and its respective aldehydes as alternate substrates. Moreover, the enzyme utilizes ethanol as a substrate in a reaction mechanism where this is subjected to a two-step oxidation process to produce acetic acid without releasing the acetaldehyde intermediary to the media. Moreover, we propose a mechanism that, under physiological conditions, might permit a massive conversion of ethanol to acetic acid, as usually occurs in the acetic acid bacteria, but without the transient accumulation of the highly toxic acetaldehyde.

Show MeSH
Related in: MedlinePlus