title: The active (ADHa) and inactive (ADHi) forms of the PQQ-alcohol dehydrogenase from Gluconacetobacter diazotrophicus differ in their respective oligomeric structures and redox state of their corresponding prosthetic groups.
abstract: The membrane-bound alcohol dehydrogenase of Gluconacetobacter diazotrophicus contains one pyrroloquinoline quinone moiety (PQQ), one [2Fe-2S] cluster, and four c-type cytochromes. Here, we describe a novel and inactive enzyme. ADHi, similarly to ADHa, is a heterodimer of 72- and 44-kDa subunits and contains the expected prosthetic groups. However, ADHa showed a threefold molecular mass as compared to ADHi. Noteworthy, the PQQ, the [2Fe-2S] and most of the cytochromes in purified ADHi is in the oxidized form, contrasting with ADHa where the PQQ-semiquinone is detected and the [2Fe-2S] cluster as well as the cytochromes c remained fully reduced after purification. Reduction kinetics of the ferricyanide-oxidized enzymes showed that while ADHa was brought back by ethanol to its full reduction state, in ADHi, only one-quarter of the total heme c was reduced. The dithionite-reduced ADHi was largely oxidized by ubiquinone-2, thus indicating that intramolecular electron transfer is not impaired in ADHi. The acidic pH of the medium might be deleterious for the membrane-bound ADH by causing conformational changes leading to changes in the relative orientation of heme groups and shift of corresponding redox potential to higher values. This would hamper electron transfer resulting in the low activity observed in ADHi.
authors.affiliation: Laboratorio de Bioquímica-Genética, Torre de Investigación, Instituto Nacional de Pediatría.
authors.forename: Saúl
authors.initials: S
authors.lastname: Gómez-Manzo
authors.forename: Alejandra Abigail
authors.initials: AA
authors.lastname: González-Valdez
authors.forename: Jesús
authors.initials: J
authors.lastname: Oria-Hernández
authors.forename: Horacio
authors.initials: H
authors.lastname: Reyes-Vivas
authors.forename: Roberto
authors.initials: R
authors.lastname: Arreguín-Espinosa
authors.forename: Peter M H
authors.initials: PM
authors.lastname: Kroneck
authors.forename: Martha Elena
authors.initials: ME
authors.lastname: Sosa-Torres
authors.forename: Jose E
authors.initials: JE
authors.lastname: Escamilla
mesh_terms: D000143:Acids / Q000737:chemistry; D000426:Alcohol Dehydrogenase / Q000737:chemistry*; D002462:Cell Membrane / Q000737:chemistry; D003470:Culture Media / Q000737:chemistry; D045304:Cytochromes c / Q000737:chemistry; D004579:Electron Transport; D004789:Enzyme Activation; D057075:Enzyme Assays; D000431:Ethanol / Q000737:chemistry; D041821:Gluconacetobacter / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D008970:Molecular Weight; D010084:Oxidation-Reduction; D045542:PQQ Cofactor / Q000737:chemistry*; D011487:Protein Conformation; D017186:Titrimetry / Q000379:methods; D014451:Ubiquinone / Q000737:chemistry
chemical_list: D000143:Acids; D003470:Culture Media; D014451:Ubiquinone; D000431:Ethanol; D045542:PQQ Cofactor; D045304:Cytochromes c; D000426:Alcohol Dehydrogenase; C025204:Ubiquinone Q2