The PQQ-alcohol dehydrogenase of Gluconacetobacter diazotrophicus.
The oxidation of ethanol to acetic acid is the most characteristic process in acetic acid bacteria. Gluconacetobacter diazotrophicus is rather unique among the acetic acid bacteria as it carries out nitrogen fixation and is a true endophyte, originally isolated from sugar cane. Aside its peculiar life style, Ga. diazotrophicus, possesses a constitutive membrane-bound oxidase system for ethanol. The Alcohol dehydrogenase complex (ADH) of Ga. diazotrophicus was purified to homogeneity from the membrane fraction. It-exhibited two subunits with molecular masses of 71.4 kDa and 43.5 kDa. A positive peroxidase reaction confirmed the presence of cytochrome c in both subunits. Pyrroloquinoline quinone (PQQ) of ADH was identified by UV-visible light and fluorescence spectroscopy. The enzyme was purified in its full reduced state; potassium ferricyanide induced its oxidation. Ethanol or acetaldehyde restored the full reduced state. The enzyme showed an isoelectric point (pI) of 6.1 and its optimal pH was 6.0. Both ethanol and acetaldehyde were oxidized at almost the same rate, thus suggesting that the ADH complex of Ga. diazotrophicus could be kinetically competent to catalyze, at least in vitro, the double oxidation of ethanol to acetic acid.
Gómez-Manzo
Saúl
S
Departamento de Bioquímica, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad Universitaria, A. P. 70242, México, D.F. 04510, México.
Contreras-Zentella
Martha
M
González-Valdez
Alejandra
A
Sosa-Torres
Martha
M
Arreguín-Espinoza
Roberto
R
Escamilla-Marván
Edgardo
E
D019342:Acetic Acid / Q000378:metabolism*; D000426:Alcohol Dehydrogenase / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D000431:Ethanol / Q000378:metabolism; D005516:Food Microbiology; D041821:Gluconacetobacter / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D007526:Isoelectric Point; D008970:Molecular Weight; D009584:Nitrogen / Q000378:metabolism*; D009586:Nitrogen Fixation; D010084:Oxidation-Reduction; D045542:PQQ Cofactor / Q000378:metabolism*
D000431:Ethanol; D045542:PQQ Cofactor; D000426:Alcohol Dehydrogenase; D009584:Nitrogen; D019342:Acetic Acid