According to current knowledge the most common mechanism of enzymatic activation of n-alkanes in the absence of molecular oxygen, i.e. in anaerobic bacteria, is the addition of the substrate to fumarate catalyzed by the glycyl radical enzyme (methylalkyl)succinate synthase [1]. Experiments with stereoselectively deuterated n-hexane derivatives revealed the stereochemistry of this unprecedented enzyme reaction and provided evidence for a concerted reaction mechanism (Scheme 1) [2]. This project seeks to provide further insights into the transformation mechanisms of saturated hydrocarbons in anaerobic bacteria. One key objective is to elucidate the structural adaptation of (methylalkyl)succinate synthases of different bacterial strains with respect to their specific chain length ranges of n-alkanes utilized. Particular attention will be paid to mechanistically understand apparent differences of succinate synthases of n-alkane- versus alkylbenzene-utilizing bacteria as revealed from experiments with substrate mixtures [3]. It is furthermore planned to investigate other less well understood mechanisms of hydrocarbon activation for which so far only preliminary evidence is available. The project may include the development of biomimetic hydrocarbon activation reactions. It is anticipated that these investigations will contribute to a better understanding of the evolution of hydrocarbon-activating enzymes. The project has a strong analytical foundation (isolation and rigid structural characterisation of metabolites using liquid and gas chromatography, mass spectrometry, NMR spectroscopy etc.) with a significant preparative component (synthesis of reference compounds and model substrates, including stable isotope labeling).

[1] H. Wilkes, W. Buckel, B. T. Golding, R. Rabus, J. Mol. Microbiol. Biotechnol. 2016, 26, 138-151.
[2] R. Jarling, M. Sadeghi, M. Drozdowska, S. Lahme, W. Buckel, R. Rabus, F. Widdel, B. T. Golding, H. Wilkes, Angew. Chem. 2012, 124, 1362-1366; Angew. Chem. Int. Ed. 2012, 51, 1334-1338.
[3] R. Jarling, S. Kühner, E. Basílio Janke, A. Gruner, M. Drozdowska, B. T. Golding, R. Rabus, H. Wilkes, Front. Microbiol. 2015, 6, DOI: 10.3389/fmicb.2015.00880.