RESUMO
Castellaniella defragrans is a Betaproteobacterium capable of coupling the oxidation of monoterpenes with denitrification. Geraniol dehydrogenase (GeDH) activity was induced during growth with limonene in comparison to growth with acetate. The N-terminal sequence of the purified enzyme directed the cloning of the corresponding open reading frame (ORF), the first bacterial gene for a GeDH (geoA, for geraniol oxidation pathway). The C. defragrans geraniol dehydrogenase is a homodimeric enzyme that affiliates with the zinc-containing benzyl alcohol dehydrogenases in the superfamily of medium-chain-length dehydrogenases/reductases (MDR). The purified enzyme most efficiently catalyzes the oxidation of perillyl alcohol (k(cat)/K(m) = 2.02 × 10(6) M(-1) s(-1)), followed by geraniol (k(cat)/K(m) = 1.57 × 10(6) M(-1) s(-1)). Apparent K(m) values of <10 µM are consistent with an in vivo toxicity of geraniol above 5 µM. In the genetic vicinity of geoA is a putative aldehyde dehydrogenase that was named geoB and identified as a highly abundant protein during growth with phellandrene. Extracts of Escherichia coli expressing geoB demonstrated in vitro a geranial dehydrogenase (GaDH) activity. GaDH activity was independent of coenzyme A. The irreversible formation of geranic acid allows for a metabolic flux from ß-myrcene via linalool, geraniol, and geranial to geranic acid.
Assuntos
Alcaligenaceae/enzimologia , Oxirredutases do Álcool/metabolismo , Aldeído Desidrogenase/metabolismo , Regulação Bacteriana da Expressão Gênica , Monoterpenos/metabolismo , Terpenos/metabolismo , Monoterpenos Acíclicos , Alcaligenaceae/genética , Alcaligenaceae/crescimento & desenvolvimento , Oxirredutases do Álcool/genética , Aldeído Desidrogenase/genética , Anaerobiose , Meios de Cultura , Escherichia coli/enzimologia , Escherichia coli/genética , Dados de Sequência Molecular , Monoterpenos/química , Análise de Sequência de DNARESUMO
The degradability of pivalic acid was established by the isolation of several facultative denitrifying strains belonging to Zoogloea resiniphila, to Thauera and Herbaspirillum, and to Comamonadaceae, related to [Aquaspirillum] and Acidovorax, and of a nitrate-reducing bacterium affiliated with Moraxella osloensis. Pivalic acid was completely mineralized to carbon dioxide. The catabolic pathways may involve an oxidation to dimethylmalonate or a carbon skeleton rearrangement, a putative 2,2-dimethylpropionyl coenzyme A mutase.