Open AccessThe active ( ADH a) and inactive ( ADH i) forms of the PQQ ‐alcohol dehydrogenase from G luconacetobacter diazotrophicus differ in their respective oligomeric structures and redox state of their corresponding prosthetic groups
Author(s) -
GómezManzo Saúl,
GonzálezValdez Alejandra Abigail,
OriaHernández Jesús,
ReyesVivas Horacio,
ArreguínEspinosa Roberto,
Kroneck Peter M.H.,
SosaTorres Martha Elena,
Escamilla Jose E.
Publication year - 2012
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.2011.02487.x
Subject(s) - chemistry , redox , alcohol dehydrogenase , pyrroloquinoline quinone , cofactor , electron transfer , moiety , biochemistry , heme , photochemistry , dehydrogenase , stereochemistry , enzyme , organic chemistry
The membrane‐bound alcohol dehydrogenase of G luconacetobacter diazotrophicus contains one pyrroloquinoline quinone moiety ( PQQ ), one [2 Fe ‐2 S ] cluster, and four c ‐type cytochromes. Here, we describe a novel and inactive enzyme. ADH i, similarly to ADH a, is a heterodimer of 72‐ and 44‐kDa subunits and contains the expected prosthetic groups. However, ADH a showed a threefold molecular mass as compared to ADH i. Noteworthy, the PQQ , the [2 Fe ‐2 S ] and most of the cytochromes in purified ADH i is in the oxidized form, contrasting with ADH a where the PQQ ‐semiquinone is detected and the [2 Fe ‐2 S ] cluster as well as the cytochromes c remained fully reduced after purification. Reduction kinetics of the ferricyanide‐oxidized enzymes showed that while ADH a was brought back by ethanol to its full reduction state, in ADH i, only one‐quarter of the total heme c was reduced. The dithionite‐reduced ADH i was largely oxidized by ubiquinone‐2, thus indicating that intramolecular electron transfer is not impaired in ADH i. 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 ADH i.