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    STUDIA BIOLOGIA - Issue no. 1 / 2019  
         
  Article:   CATABOLISM OF THE EXTREMOLYTES ECTOINE AND HYDROXYECTOINE – REGULATION AND MECHANISMS.

Authors:  LUCAS HERMANN, ERHARD BREMER. 		 
       
         
  Abstract:   Ectoine and its derivative hydroxyectoine are widely used as osmostress protectants by members of the Bacteria. A large group of Proteobacteria can metabolize these osmolytes and use them as sole carbon, nitrogen and energy sources. In the marine Roseobacter species Ruegeria pomeroyi the ectoine utilization operon consists of the core metabolic enzymes EutABC which seem to be involved in the degradation of hydroxyectoine and EutDE which catabolize ectoine. EutD opens the pyrimidine ring of ectoine to form N-α-ADABA and EutE deacetylates this intermediate to DAB which then can fuel the cells energy metabolism. The operon is tightly regulated by the GntR-type protein EnuR which binds to two specific operator sites upstream of the ectoine/ hydroxyectoine importer and catabolic gene cluster. An EnuR-K302H mutant and reduction by NaBH4 show that PLP is covalently bound by EnuR and is used to detect N-α-ADABA and DAB as inducers. This changes the DNA-binding affinity of EnuR, which is shown by EMSAs. Bioinformatic analysis suggests the widespread use and adaptations of this metabolic pathway, and therefore implicates ectoine metabolisms in global carbon and nitrogen cycles driven by bacteria.

Keywords: ectoine, GntR, hydroxyectoine, metabolism, regulation. 		 
         
     
         
         
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