Enzymatic Activation Of Alkanes Constraints And Prospects. Enzymatic Activation Of Alkanes Constraints And Prospects Lacrosse Rahim Bakar, and Zaliza Hanapi.

Abstract Hydrocarbons are abundant in anoxic environments and pose biochemical challenges to their anaerobic degradation by microorganisms. Within the framework of the Priority Program 1319, investigations funded by the Deutsche Forschungsgemeinschaft on the anaerobic microbial degradation of hydrocarbons ranged from isolation and enrichment of hitherto unknown hydrocarbon-degrading anaerobic microorganisms, discovery of novel reactions, detailed studies of enzyme mechanisms and structures to process-oriented in situ studies.

Selected highlights from this program are collected in this synopsis, with more detailed information provided by theme-focused reviews of the special topic issue on ‘Anaerobic biodegradation of hydrocarbons' [this issue, pp. The interdisciplinary character of the program, involving microbiologists, biochemists, organic chemists and environmental scientists, is best exemplified by the studies on alkyl-/arylalkylsuccinate synthases. Pure and enriched cultures of bacteria used to study anaerobic degradation of hydrocarbons coupled to nitrate, sulfate or iron reduction or to fermentative or syntrophic growth Metabolism of Aromatic Compounds Toluene-Activating Benzylsuccinate Synthase, the Archetype of Alkyl-/Arylalkylsuccinate Synthases An overview of structural and functional properties of toluene-activating benzylsuccinate synthase (BSS) and other related glycyl radical-bearing alkyl-/arylalkylsuccinate synthases is provided by Heider et al. BSS and glycyl radical enzymes in general carry a conserved glycine residue close to the C terminus of the catalytic subunit for generating an organic (glycyl) radical and a structurally close-by cysteine residue, assumed to function as reactive (thiyl) radical. The (αβγ) 2 heterohexameric and O 2-sensitive BSS is best studied in the betaproteobacterial strains Thauera aromatica K172, T. Aromatica T1 and Azoarcus sp. Strain T, and was previously shown to stereospecifically add toluene to the cosubstrate fumarate forming ( R)-benzylsuccinate.

Based on biochemical, structural and modeling data, the following mechanistic concept for the catalytic cycle of BSS has been conceived (fig. A, upper panel). Upon substrate binding (first fumarate, then toluene in a long active site cavity of BSS from T. Aromatica T1 [Funk et al., 2015]), a reactive thiyl radical (Cys 493) is generated at the expense of the spatially close-by resting-state glycyl radical (Gly 829). In the initial step controlling the reaction rate, the thiyl radical abstracts a hydrogen atom from the methyl group, yielding a first transition state (fig. The Last Story Wii Iso Undubtably. A, lower panel) with the highest energy level and subsequently an enzyme-bound benzyl radical intermediate.