quinohaemoprotein alcohol dehydrogenase from Gluconacetobacter xylinus: molecular and catalytic properties

• Published in: Archives of microbiology 2010-09, Vol.192 (9), p.703-713
• Main Authors: Chávez-Pacheco, J. L, Contreras-Zentella, M, Membrillo-Hernández, J, Arreguín-Espinoza, R, Mendoza-Hernández, G, Gómez-Manzo, S, Escamilla, J. E
• Format: Article
• Language: English
• Subjects: acetic acid bacteria; Acids; Alcohol; alcohol dehydrogenase; Alcohol Oxidoreductases - chemistry; Alcohol Oxidoreductases - metabolism; Aldehydes; Bacteria; Bacteriology; Biochemistry; Biological and medical sciences; Biomedical and Life Sciences; Biotechnology; Cell Biology; Cellulose; Cytochrome; Dehydrogenase; Dehydrogenases; Ecology; Electrons; Enzymes; Ethanol; Fundamental and applied biological sciences. Psychology; Gluconacetobacter xylinus; Gluconacetobacter xylinus - enzymology; Heme - analogs & derivatives; Heme - chemistry; Hydrogen-Ion Concentration; Life Sciences; Liquid chromatography; Microbial Ecology; Microbiology; Miscellaneous; Original Paper; Oxidation; Oxidation-Reduction; Physiology; PQQ Cofactor - chemistry; Substrate Specificity
• ISSN: 0302-8933; 1432-072X
• DOI: 10.1007/s00203-010-0598-0

Gluconacetobacter xylinus possesses a constitutive membrane-bound oxidase system for the use of ethanol. Its alcohol dehydrogenase complex (ADH) was purified to homogeneity and characterized. It is a 119-kDa heterodimer (68 and 41 kDa subunits). The peroxidase reaction confirmed the presence of haem C in both subunits. Four cytochromes c per enzyme were determined by pyridine hemochrome spectroscopy. Redox titrations of the purified ADH revealed the presence of four haem c redox centers, with apparent mid-point potential values (Em₇) of −33, +55, +132 and +310 mV, respectively. The ADH complex contains one mol of pyrroloquinoline quinone as determined by HPLC. The enzyme was purified in full reduced state; oxidation was induced by potassium ferricyanide and substrate restores full reduction. Activity responses to pH were sharp, showing two distinct optimal pH values (i.e. pH 5.5 and 6.5) depending on the electron acceptor used. Purified ADH oxidizes primary alcohols (C2-C6) but not methanol. Noteworthy, aliphatic aldehydes (C1-C4) were also good substrates. Myxothiazol and antymicin A were powerful inhibitors of the purified ADH complex, most likely acting at the ubiquinone acceptor site in subunit II.