l‐Rhamnose catabolism in archaea

• Published in: Molecular microbiology Vol. 111; no. 4; pp. 1093 - 1108
• Main Authors: Reinhardt, Andreas, Johnsen, Ulrike, Schönheit, Peter
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01.04.2019
• Subjects: ABC transporter; Archaea; ATP-Binding Cassette Transporters - metabolism; Carbohydrate Dehydrogenases - metabolism; Carbohydrate Metabolism; Catabolism; Degradation; Dehydration; Dehydrogenase; Dehydrogenases; Energy sources; Enzymes; Genes; Genes, Archaeal; Haloferax volcanii - enzymology; Haloferax volcanii - genetics; Hydrolase; Lactic acid; Multigene Family; Oxidoreductases - metabolism; Pyruvic acid; Rhamnose; Rhamnose - metabolism; Sulfolobus solfataricus - genetics; Sulfolobus solfataricus - metabolism; Transcription
• ISSN: 0950-382X; 1365-2958; 1365-2958
• DOI: 10.1111/mmi.14213

Summary The halophilic archaeon Haloferax volcanii utilizes l‐rhamnose as a sole carbon and energy source. It is shown that l‐rhamnose is taken up by an ABC transporter and is oxidatively degraded to pyruvate and l‐lactate via the diketo‐hydrolase pathway. The genes involved in l‐rhamnose uptake and degradation form a l‐rhamnose catabolism (rhc) gene cluster. The rhc cluster also contains a gene, rhcR, that encodes the transcriptional regulator RhcR which was characterized as an activator of all rhc genes. 2‐keto‐3‐deoxy‐l‐rhamnonate, a metabolic intermediate of l‐rhamnose degradation, was identified as inducer molecule of RhcR. The essential function of rhc genes for uptake and degradation of l‐rhamnose was proven by the respective knockout mutants. Enzymes of the diketo‐hydrolase pathway, including l‐rhamnose dehydrogenase, l‐rhamnonolactonase, l‐rhamnonate dehydratase, 2‐keto‐3‐deoxy‐l‐rhamnonate dehydrogenase and 2,4‐diketo‐3‐deoxy‐l‐rhamnonate hydrolase, were characterized. Further, genes of the diketo‐hydrolase pathway were also identified in the hyperthermophilic crenarchaeota Vulcanisaeta distributa and Sulfolobus solfataricus and selected enzymes were characterized, indicating the presence of the diketo‐hydrolase pathway in these archaea. Together, this is the first comprehensive description of l‐rhamnose catabolism in the domain of archaea. Here, we present a comprehensive analysis of l‐rhamnose catabolism in the halophilic euryarchaeon Haloferax volcanii. In this archaeon, l‐rhamnose is taken up by an ABC transporter and is degraded via the diketo‐hydrolase pathway that is regulated by the bacterial like transcriptional activator RhcR. Further evidence is presented for the operation of the diketo‐hydrolase pathway in the hyperthermophilic crenarchaeota Sulfolobus solfataricus and Vulcanisaeta distributa.