Genes and enzymes involved in the biodegradation of the quaternary carbon compound pivalate in the denitrifying Thauera humireducens strain PIV-1

Christian Jacoby, Christa Ebenau-Jehle, Katharina Saum, Nico Jehmlich, Martin von Bergen, Thomas Brüls, Matthias Boll

Quaternary carbon-containing compounds exist in natural and fossil oil-derived products and are used inchemical and pharmaceutical applications up to industrial scale. Due to the inaccessibility of the quaternary carbon atom for a direct oxidative or reductive attack, they are considered as persistent in the environment. Here, we investigated the unknown degradation of the quaternary carbon-containing model compound pivalate (2,2-dimethyl-propionate) in the denitrifying bacterium Thauera humireducens strainPIV-1 (formerly Thauera pivalivorans). We provide multiple evidence for a pathway comprising the activationto pivalyl-CoA and the carbon skeleton rearrangement to isovaleryl-CoA. Subsequent reactions proceed similar to the catabolic leucine degradation pathway such as the carboxylation to 3-methylglutaconyl-CoA and the cleavage of 3-methyl-3-hydroxyglutaryl-CoA to acetyl-CoA and acetoacetate..