The inactive and active forms of the pyrroloquinoline quinone-alcohol dehydrogenase of Gluconacetobacter diazotrophicus: a comparative study

Gluconacetobacter diazotrophicus as a member of the acetic acid bacteria group, oxidize alcohol to acetic acid through two sequential reactions catalyzed by the alcohol dehydrogenase (ADH) and the aldehyde dehydrogenase, both enzymes are membrane-bound and oriented to the periplasmic space. ADH is a quinohemoprotein carrying one pyrroloquinoline quinone moiety, one [2Fe:2S] cluster and four c-type cytochromes, as prosthetic groups. In recent years has been described the presence of the inactive ADH (ADHi) in the acetic acid bacteria. In the present review we make a comparative study of the molecular and catalytic properties of the active and inactive forms of ADH purified from G. diazotrophicus, variation in the redox state of enzymes as purified could explain the notorious differences seen in the activity power of the compared enzymes.