Functional characterization of propane-enhanced N-nitrosodimethylamine degradation by two actinomycetales. Academic Article uri icon


  • Propane-induced cometabolic degradation of n-nitrosodimethylamine (NDMA) by two propanotrophs is characterized through kinetic, gene presence, and expression studies. After growth on propane, resting cells of Rhodococcus sp. RR1 possessed a maximum transformation rate (v(max,n)) of 445gNDMA(mgprotein)(-1)h(-1); the rate for Mycobacterium vaccae (austroafricanum) JOB-5 was modestly lower with v(max,n) of 283gNDMA(mgprotein)(-1)h(-1). Both strains were capable of degrading environmentally relevant, trace quantities of NDMA to below the experimental limit of detection, calculated as 20ngNDMAL(-1). However, a comparison of half saturation constants (K(s,n)) and NDMA degradation in the presence of propane revealed pronounced differences between the strains. The K(s,n) for strain RR1 was 3610gNDMAL(-1) while the propane concentration needed to inhibit NDMA rates by 50% (K(inh)) occurred at 7,700gpropaneL(-1) (R(2)=0.9669). In contrast, strain JOB-5 had a markedly lower affinity for NDMA verses propane with a calculated K(s,n) of 2,2001,000gNDMAL(-1) and K(inh) of 120gpropaneL(-1) (R(2)=0.9895). Genomic and transcriptional investigations indicated that the functional enzymes involved in NDMA degradation and propane metabolism are different for each strain. For Rhodococcus sp. RR1, a putative propane monooxygenase (PrMO) was identified and implicated in NDMA oxidation. In contrast, JOB-5 was not found to possess a PrMO homologue and two functionally analogous alkane monoxygenases (AlkMOs) were not induced by growth on propane. Differences between the PrMO in this Rhodococcus and the unidentified enzyme(s) in the Mycobacterium may explain differences in NDMA degradation and inhibition kinetics between these strains.

published proceedings

  • Biotechnol Bioeng

author list (cited authors)

  • Sharp, J. O., Sales, C. M., & Alvarez-Cohen, L.

citation count

  • 34

complete list of authors

  • Sharp, Jonathan O||Sales, Christopher M||Alvarez-Cohen, Lisa

publication date

  • December 2010