The enzyme is part of the biosynthesis pathway of the sialic acid 3-deoxy-D-glycero-¦Â-D-galacto-non-2-ulopyranosonate (Kdn). Kdn is abundant in extracellular glycoconjugates of lower vertebrates such as fish and amphibians, but is also found in the capsular polysaccharides of bacteria that belong to the?Bacteroides?genus.