Identification and characterization of 2‐naphthoyl‐coenzyme A reductase, the prototype of a novel class of dearomatizing reductases

• Published in: Molecular microbiology Vol. 88; no. 5; pp. 1032 - 1039
• Main Authors: Eberlein, Christian, Estelmann, Sebastian, Seifert, Jana, von Bergen, Martin, Müller, Michael, Meckenstock, Rainer U., Boll, Matthias
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01.06.2013
• Subjects: Adenosine triphosphatase; Anaerobiosis; Biotransformation; Carboxylic Acids - metabolism; Coenzyme A - metabolism; Coenzymes - metabolism; E coli; Electrons; Environmental Microbiology; Enzymes; Escherichia coli - genetics; Flavin Mononucleotide - metabolism; Flavin-Adenine Dinucleotide - metabolism; Iron-Sulfur Proteins; Molecular Weight; Naphthalenes - metabolism; Oxidoreductases - chemistry; Oxidoreductases - genetics; Oxidoreductases - isolation & purification; Oxidoreductases - metabolism; Polycyclic aromatic hydrocarbons; Protein Multimerization; Recombinant Proteins - genetics; Recombinant Proteins - metabolism
• ISSN: 0950-382X; 1365-2958
• DOI: 10.1111/mmi.12238

Summary The enzymatic dearomatization of aromatic ring systems by reduction represents a highly challenging redox reaction in biology and plays a key role in the degradation of aromatic compounds under anoxic conditions. In anaerobic bacteria, most monocyclic aromatic growth substrates are converted to benzoyl‐coenzyme A (CoA), which is then dearomatized to a conjugated dienoyl‐CoA by ATP‐dependent or ‐independent benzoyl‐CoA reductases. It was unresolved whether or not related enzymes are involved in the anaerobic degradation of environmentally relevant polycyclic aromatic hydrocarbons (PAHs). In this work, a previously unknown dearomatizing 2‐naphthoyl‐CoA reductase was purified from extracts of the naphthalene‐degrading, sulphidogenic enrichment culture N47. The oxygen‐tolerant enzyme dearomatized the non‐activated ring of 2‐naphthoyl‐CoA by a four‐electron reduction to 5,6,7,8‐tetrahydro‐2‐naphthoyl‐CoA. The dimeric 150 kDa enzyme complex was composed of a 72 kDa subunit showing sequence similarity to members of the flavin‐containing ‘old yellow enzyme’ family. NCR contained FAD, FMN, and an iron‐sulphur cluster as cofactors. Extracts of Escherichia coli expressing the encoding gene catalysed 2‐naphthoyl‐CoA reduction. The identified NCR is a prototypical enzyme of a previously unknown class of dearomatizing arylcarboxyl‐CoA reductases that are involved in anaerobic PAH degradation; it fundamentally differs from known benzoyl‐CoA reductases.