Geraniol and Geranial Dehydrogenases Induced in Anaerobic Monoterpene Degradation by Castellaniella defragrans

Abstract

ABSTRACTCastellaniella defragransis aBetaproteobacteriumcapable 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, forgeranioloxidation pathway). TheC. defragransgeraniol 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 (kcat/Km= 2.02 × 106M−1s−1), followed by geraniol (kcat/Km= 1.57 × 106M−1s−1). ApparentKmvalues of <10 μM are consistent with anin vivotoxicity of geraniol above 5 μM. In the genetic vicinity ofgeoAis a putative aldehyde dehydrogenase that was namedgeoBand identified as a highly abundant protein during growth with phellandrene. Extracts ofEscherichia coliexpressinggeoBdemonstratedin vitroa geranial dehydrogenase (GaDH) activity. GaDH activity was independent of coenzyme A. The irreversible formation of geranic acid allows for a metabolic flux from β-myrcene via linalool, geraniol, and geranial to geranic acid.