Inger Lin Uttakleiv Ræder, M.K Gurung, B. Altermark, T.O Berg, R. Helland and A.O. Smalås
Sialic acids are 9-carbon sugars found associated with both bacterial and eukaryotic cells. They are important for cell-cell communication, pathogen interaction and immune recognition. The genome of the psychrophilic and fish pathogenic bacterium Aliivibrio salmonicida reveals that it possesses the ability to synthesize two sialic acids, Neuraminic and Legionaminic acid. We have recombinantly produced several of the proteins belonging to these pathways and characterization is ongoing. A sialic acid aldolase from A. salmonicida and a sialic acid synthase from the psychrophilic and fish pathogenic bacterium Moritella viscosa are also targeted. Three protein structures have been solved. Characterization of the enzymes and the catalytic pathways is important for understanding their role in pathogenesis and for exploiting their application potential. The determination of 3D-structures, catalytic mechanisms and substrate preferences pave the way for design of inhibitors blocking the infection ability of the bacteria, and can be helpful for designing tailored enzymes for production of sialic acids. The synthesis of natural and modified sialic acids is important because of their highly applicable properties as use in a wide range of medical applications and as glyconutrients (Figure). Enzymes from a psychrophile with cold active features are also particularly relevant as targets for commercial exploitation.