An inducible 1-butanol dehydrogenase, a quinohaemoprotein, is involved in the oxidation of butane by 'Pseudomonas butanovora'

Butane-grown 'Pseudomonas butanovora' expressed two soluble alcohol dehydrogenases (ADHs), an NAD(+)-dependent secondary ADH and an NAD(+) independent primary ADH. Two additional NAD+-dependent secondary ADHs could be detected when cells were grown on 2-butanol and lactate. The inducible NAD(+)-independent 1-butanol dehydrogenase (BDH) of butane-grown cells was primarily responsible for 1-butanol oxidation in the butane metabolism pathway. BDH was purified to near homogeneity and identified as a quinohaemoprotein, containing, per mol enzyme, 1.0 mol pyrroloquinoline quinone (PQQ) and 0.25 mol haem c as prosthetic groups. BDH was synthesized as a monomer of approximately 66 kDa. It has a broad substrate range, including primary alcohols, secondary alcohols, aldehydes, C-4 diols and aromatic alcohols. It exhibited the lowest K-m (7+/-1 muM) and highest k(cat)/K-m (72 x 10(4) M-1 s(-1)) value towards l-butanol. BDH exhibited ferricyanide-dependent ADH activity. Calcium ions (up to 10 mM) increased BDH activity substantially. Two BDH internal amino acid sequences showed 73 and 62% identity and 83 and 66% similarity, respectively, when compared with an amino acid sequence of ethanol dehydrogenase from Comamonas testosteroni. The presence of the inducible BDH and secondary ADH may indicate that the terminal and subterminal oxidation pathways are involved in butane degradation of butane-grown 'P. butanovora'.